Computer Expert Witness
Graham Dilloway CITP MBCS
Computer Expert Witness

Chartered IT Professional and Member of British Computer Society

Listed in Register of Expert Witnesses

Member of the Academy of Experts

View Graham Dilloway's profile on LinkedIn

Hard Drive Failure

The Claimant, Mr C, bought a laptop computer from the Defendant, Company D.  The hard disk in the computer failed after twenty-six months.  Company D supplied two replacement disks and Mr C was unable to get either disk to operate correctly in the computer.

My IT expert report discusses the reliability to be expected from computer components and the technical and other issues involved with the replacement of the hard disk in a laptop computer.

Note:    This expert witness report is reproduced exactly as it was when served excepting that company and personal names have been removed.


1. This report was prepared by Graham Dilloway of 39 Conham Hill Bristol BS15 3AW. I am a Member of the British Computer Society, the chartered professional body for the computer industry in the UK. I am a member of the Academy of Experts and of the Expert Witness Institute. I have worked with computers for 30 years. This work has all involved the implementation and configuration of computers, their operating systems and the core software applications of a computer environment (e.g. word processors and spreadsheets). I have worked with personal computers almost exclusively for more than fifteen years.


2. My instructions are contained in an email from Solicitor S dated 24 July 2002:
" Please can you provide your view as computer expert on the following:-
1. On the balance of probabilities, the likely cause of the problem experienced by Mr C and whether he could have obtained a replacement hard disk. If you are aware that he could have, please state the suppliers.
2. If, on the balance of probabilities, and in view of the timing of the hard disc allegedly crashing, the cause of the hard disc allegedly "crashing" was because the computer was of unsatisfactory quality."

3. This report is based upon information contained in the bundle of documents sent with the email from Solicitor S dated 24 July 2002. The email describes these documents as:
"1. extract of communications between Solicitor S and Solicitors for the Claimant (in reverse chronological order).
2. copy communications between the Claimant and Defendant Company D.
3. copy pleadings (statements of case as they are now known)."

4. I have not seen the computer or either of the replacement hard disks.

Hard Disk Failure in a Laptop Computer

5. The laptop computer was purchased in July 1996. The hard disk failed in September 1998

6. In his letter to Company D dated 26 October 1998, Mr C describes his conversations with Company D technical support. The letter says that the conversations occurred on 1 October 1998 and mentions a hard disk problem as the only issue.

7. It is my opinion that the reliability and longevity to be expected from computers is the same as would be expected from other domestic appliances such as, for example, washing machines.

8. The suppliers of computers and the suppliers of, for example, washing machines offer extended warranties. It may be that the availability of these warranties for computers and for domestic appliances indicates that customers should take a similar view regarding the reliability and longevity to be expected from computers and from other domestic appliances.

9. I have worked for many large companies (for example, NatWest, Orange and BAe) during projects that have required the acquisition of computers. It is a widely held view within these companies that every computer should have a hardware service contract that takes effect when the initial warranty expires. These hardware service contracts are the equivalent to the extended warranties offered to individual consumers. It may be that the use of hardware service contracts by large companies indicates that individual consumers should buy extended warranties for computers that are of particular importance.

10. The hard disks installed in computers are mechanical devices that contain moving parts. It may be reasonable to expect that a component that contains moving parts is more likely to fail than a component, such as a circuit board, that does not.

11. I found nothing in the correspondence between Mr C and Company D to indicate a specific cause for the failure of the hard disk.

12. I would be disappointed, but not surprised, if a computer hard disk or a washing machine motor failed after 26 months.

13. Most versions of the Windows operating system include backup software. The version of Windows (2000) that is on the computer that I am using includes help text that says of backup, in part, "The Backup utility helps you create a copy of the data on your hard disk. In the event that the original data on your hard disk is accidentally erased or overwritten, or becomes inaccessible because of a hard disk malfunction, you can use the copy to restore your lost or damaged data."

14. It is my opinion that Windows includes backup software because there is a widely held view that hard disks may fail and customers expect software suppliers to provide tools to minimise the impact of a failure.

Replacement of Hard Disk in a Laptop Computer

15. Appendix A of this report contains part of the web page at and describes the replacement of the hard disk in a laptop computer.

16. Almost all laptop hard disks are the same size and have the same electrical connector (the socket that allows data and electricity to get in and out of the drive). However, most laptop makers put the drives into a caddy (a metal case or cage) that allows the drive to be more easily inserted into and removed from the computer. The caddy sometimes includes a "special" electrical connector to ease insertion and removal. The "special" electrical connector plugs into the standard connector of the drive on one side and into a possibly non-standard connector of the computer on the other side.

17. Replacing the hard disk in a laptop computer usually requires the old disk to be removed from the caddy. The caddy can then be re-used with the new disk.

18. Appendix A of this report includes a section headed, "Special notes for notebook computers made prior to 1998" that describes a change to the positions of the screw holes used to attach a hard disk to a caddy. I have seen several Internet websites that contain information about this change and that suggest methods for inserting a newer disk into an older computer. These methods include;

19. I have not seen the computer or replacement disks in this case and cannot say whether there is a problem with the position of the screw holes. I am confident that any such problem can be easily rectified.

20. Appendix B includes pictures of laptop computer hard disks from and

21. Appendix B shows how the standard connector on a laptop computer hard disk is encased in a caddy.

Obtaining a Replacement Hard Disk for a Laptop Computer

22. Anyone can obtain information about suppliers of hard drives for laptop computers from any high street computer retailer, computer repair shop or from the Internet. I have acquired computer equipment from and consider them to be a reliable supplier. lists some hard disks that are available for laptop computers.

23. Clicking on the information symbol ( i ) at the website by the reference to the GAP 30.0GB UDMA100 disk opens a page that includes a specification for this disk. The specification includes:


Port(s) / Connector(s) Required

1 x storage DMA/ATA-100 (Ultra) / 44 PIN IDC female - 1



24. The reference to "connectors required" in the specification is a reference to the standard laptop computer hard disk connector.

25. A purchaser of this disk from would be able to insert the disk into the caddy that contains the old hard disk and insert the disk and caddy assembly into a laptop computer.

26. I have not attempted to ascertain who could supply laptop computer hard disks in 1998. It is my recollection that I was a customer of before 1998 and from that recollection I believe them to be able to supply laptop computer hard disks.


27. Computer components and washing machine components usually last for many years but some do not.

28. It is no more remarkable that a computer hard disk should fail after 26 months than it is that a washing machine motor should fail after 26 months.

29. The hard disks used in laptop computers usually conform to standards governing their size and electrical connections. Almost any disk made for laptop computers can be fitted in almost any laptop computer.

30. The hard disks used in laptop computers are usually held in a caddy that usually needs to be transferred from the old disk to the new disk when the disk is replaced. It may be necessary to take a simple additional step if the screw holes on the caddy and the disk do not align.

31. are able to supply a replacement hard disk for a laptop computer and it is my recollection that would have been able to supply a replacement hard disk for the laptop computer in question in 1998.

32. I understand my duty to the Court and I confirm that I have complied with and will continue to comply with that duty.

33. I confirm that insofar as the facts stated in my report are within my own knowledge I have made it clear which they are and I believe them to be true, and that the opinions I have expressed represent my true and complete professional opinion.

Graham Dilloway
Expert Witness

25 July 2002

39 Conham Hill


BS15 3AW



Appendix A


What do I need to know about hard drive installation ?

1. Important : Disconnect power from your notebook computer system & Remove the internal battery before beginning installation !!

2. Reuse your old hard drive caddy and adapter.
Most laptop / Notebook computers use caddy to hold hard drives. What is a caddy ? In the simplest language, it is the framework that holds the hard drive inside the notebook. Bare hard drive are not normally secured to the notebook or laptop to hold it in place. A metal or plastic device of some kind (caddy) is secured to the hard drive or in some cases totally encases the hard drive. The caddy is therefore the anchor that holds the hard drive in the notebook computer. When you purchase a new bare hard drive from us to replace your old one, you need reuse the caddy from the old hard drive. The bare notebook hard drive connector is 44-pin connector. Some notebook computers use some adapter to convert this 44-pin connector to a different type connector, in that case, you need reuse the adapter from old hard drive also.

3. Third party software may need for some old notebook computers
Some old notebooks computers are limited to accessing hard drives with a capacity of 8.4GB or less (7.9GB on some systems). 3rd party software is available that breaks the "capacity barrier". Some suggestions are EZ Drive by Micro House and Disk Manager™ DiskGo by Ontrack. But if your current notebook hard drive is already bigger than 8.4GB, then you have no problem to replace it with this hard drive, no extra software needed.

For IBM brand notebook hard drive, you can download Ontrack's Disk Manger for IBM at no charge from the following web site

4. Partition & Format New Hard Drive
New hard drive need to be partitioned and formated before loading any software. For how to partition and format new hard drive, please see the manual of your operating system software

Caution: Your Hard Disk Drive is a precision device and even a small drop onto any surface can cause damage. Electrostatic discharge can also damage the drive. You should ground yourself prior to handling the drive.

Installation Notes

· The drive should be mounted carefully on the surface of 0.1mm or less flatness to avoid excessive distortion.

· In order to prevent short-circuit under any circumstances, a space of 0.5mm or more should be kept under the PCB.

· Space should be kept around the drive to avoid any contact with other parts, which may occur due to shock or vibration.

· The temperature of the top cover and the base must always be kept under 60ƒC to maintain the required reliability.

· Be sure not to cover the breathing hole to keep the pressure inside the drive at a certain level.

· Do not apply any force to the top cover, except the screw areas on top cover. Maximum force to the specified area is 2N.

· The drive contains several parts which may be easily damaged by ESD (Electrostatic Discharge). Avoid touching the interface connector pins and the surface of PCB. Be sure to use ESD proof wrist strap when handling drive.

· The four mounting screws should be tightened equally with 0.3N-m (3kgf-cm) torque. The depth should be 3.0mm minimum and 3.5mm maximum.

Important Note: Disconnect power from your computer system before beginning installation !!

· The thickness of the hard drive is a factor in selecting both the caddy and the hard drive. 90% of the notebooks computer built today will take the 12.7mm thickness. The latest trend in new hard drives towards the 9.5mm & 8.5mm thickness which will mount and work in a 12.7mm caddy


Special notes for notebook computers made prior to 1998

In most notebooks or laptops the hard drive mounting pattern, generally eight screw holes, four on the bottom and two on each side, are used to hold the hard drive on or in the caddy. Hard drives made prior to 1998 may have had three screw holes on the sides and two of them were no more than 1 1/2 inches apart. All of the hard drive manufactures agreed on a new mounting hole pattern for 1998 and newer hard drives. This new pattern places the screw holes to within 1/2 inch of each end of the drive, long wise. This pattern places the mounting screw pattern 3 inches apart, long wise.

Notebook and laptop computers made prior to 1998 may require a new caddy when upgrading to hard drives manufactured in 1998 or later. All of the new caddies are built to accommodate the new mounting hole pattern. Generally speaking, the smallest hard drive(capacity in megabytes) with the new mounting hole pattern is a 2.1 Gb.


Appendix B


Laptop hard drive connectors in expert witness report

Underside of a 2.5" form factor notebook hard drive.
You can see the main connector, with its two rows of
22 pins (the second row is hard to see). On the right
are two more pins which are used for jumpers.
To see what this drive looks like in a caddy, complete
with its single attachment connector, see this page

The above shows a "naked" hard disk without its caddy when viewed from underneath. The pins that are visible are the standard connector used on hard disks for laptop computers.


Laptop hard drive in caddy in expert witness report

An 8.4 GB, 2.5" form factor IBM hard disk from my
notebook. Note the single connector in the front, which is
mated to a matching connector in the laptop's hard disk bay.
This allows the drive to be easily replaced at a later time.
The connector on the hard disk itself just uses straight pins
like a 3.5" hard disk form factor drive; the drive is
mounted into a carrier here, and the thin circuit board
you can see in the front "adapts" the regular pin connector
into the single Centronics-style connector my notebook uses.

The above shows a hard disk in its caddy when viewed from above. The caddy is the silver metal with the two cross head screws. The connector that is visible connects directly to the standard connector that is visible in the previous picture.