What do you do when your computer won't start or continually restarts, maybe with a blue error screen (the dreaded Blue Screen of Death (BSOD)).

The most important thing is DON'T PANIC!

Hopefully all your valuable documents, photos and videos are safely backed up....

Or maybe not, although of course you intended to get round to it.

As I said before the important thing is not to panic. In most cases your data is still safe. It is quite likely that the operating system has just got itself in a bit of a muddle and that your data is still intact.

Whatever you do don't quickly rush off looking for the recovery CD that came with your computer. Often what this will do is completely wipe off all your data and re-install the operating system exactly as it was when you first bought your PC. That is without your data!

Even if you computer is under warranty you have to be careful as in some cases if you send your computer to be repaired under warranty it will come back as good as new with a clean install, but again without your data. You need to make sure to ask what will happen to your data before sending your PC for repair.

If this is sounding a bit scary to you then maybe you need some advice. You computer manufacturer will have a helpline by all means contact them. The Internet is a great place to find advice, but of course sometimes the advice is conflicting. You may have a knowledgeable friend, which is great, if you are confident they really do know what they are talking about. Or you can visit one of the big computer stores. Finally you could consider a data recovery company, but they can be expensive, so are not normally used unless the data is irreplaceable or highly valuable.

Or of course you can speak to a local computer expert preferably one who has been recommended to you.

If someone contacts me with a PC which won't boot up properly the first thing I will do is to determine if their data is backed up and if not how valuable or important the data is. Some people are happy just to have the operating system re-installed without keeping their data.

Very often the data on the hard disk can still be read. In this case I would make a complete copy of the hard disk before attempting recovery, or at least copy the important files that the customer wants to keep.

If you are running Windows XP and the file structure is essential intact than the PC can be booted from a Windows XP CD into the recovery console. Here it is possible to run several recovery programs that will often repair problems. For example the chkdsk /r command with run a program that checks the data on the disk and attempts to repair any problems found including repairing bad sectors on the disk.

Note. Although running programs from the Windows Repair Console will often resolve problems, under certain circumstances running chkdsk or other diagnostic programs could make things worse. It is up to the individual to determine how important their data is before attempting to repair the problem themselves. The author will not accept any responsibility for problems occurring and anyone following this advice does so at their own risk.

Other data recovery programmes can be used which will either resolve disk problems or allow data to be extracted from damaged disks.

If your hard disk is not detected by the computer then you may have a hardware problem with the hard disk itself. Under these circumstances I would recommend connecting the hard disk to another know good computer with a different cable to make sure that it is not a problem with the computer main board or an incorrect BIOS setting.

At this stage most people would choose to give up and buy a new hard disk. Prices have dropped and it is very likely that you could buy a much bigger and faster hard disk relatively inexpensively. However if your data is not backed up then you may consider trying to fix the hard disk.

In the event of a problem with the hard disk itself the problem could be caused by a fault with the disks controller board. For example SATA drives have relatively delicate connector that can be damaged by rough handling. Replacement boards are available from sources such as Ebay. Great care must be taken to ensure the correct board is used and that anti-static precautions are taken to avoid damaging the board. As stated before anyone attempting this does so at their own risk.

For valuable data recovery companies can often recover data from even the most damaged hard disk. Their services are however not cheap as they have specialist knowledge, require specialist equipment and have to operate in dust free environments.