Microsoft has this fairly quick RAM test:

http://oca.microsoft.com/en/windiag.asp

It sounds like a heat issue which could be generated from RAM; CPU; Graphics chips; or Hard drive.
Do you notice abnormal heat?

Also: look in your Event viewer: rt. click My Computer then click Manage then Event Viewer.
Or: Administrative Tools/Event Viewer or Start/Run/ eventvwr
Open the system as well as the application tabs & look for X errors. Click error line for details.
Post back the source & event id especially of errors that seem to coincide with a crash.

Also view your Error Log via:
[1] Start Menu
[2] Help and Support
[3] Pick a Task
[4] Tools
[5] Advanced System Information
[6] View the Error Log

Do you get the same error on every shutdown?

I can't load anything. Basically the only thing I can do is run MS-DOS. No Operating System runs so I can't un any program, nor open 'My Computer' etc.
Is there a check I can do in MS-DOS from a boot disk??

As to a RAM test this basic version from Microsoft:

http://oca.microsoft.com/en/windiag.asp

This detailed version from MemTest:

http://www.memtest86.com/

Both run from boot floppies. The MS is quick the MemTest is not. Don't know how long the computer will run

You can also create a boot floppy diagnostic for your hard drive depending on the manufacturer: List here: http://www.tacktech.com/display.cfm?ttid=287

The next to last thought is to flash the BIOS if we can find the proper BIOS.
I am only coming up with a registration page at the moment:
http://www.vaio-link.com/downloads/r...ister.asp?l=en

I cannot run any programs in DOS exept:

Format
Fdisk

Sometimes when I do go into DOS (via a boot disk) it doesn't pick up that a hard drive is there!!!

These RAM tests & hard drive diagnostics are self booting programs.
If the floppy drive boots they should run. Even without a hard drive.

I would suggest trying to flash your BIOS. To find the latest version you would need to go thru this process:

http://www.vaio-link.com/downloads/r...ister.asp?l=en

A BIOS corruption would show the symptoms that you describe. Also Heat from a power supply issue. Also bad RAM.
As posted in post #9 the instructions for removing/replacing RAM.

...sorry - should update you. It appears that it is the hard drive that is completely corrupt.

The boot sector was dead.

SO NEW HARD DRIVE - which arrives in a couple of days.

Thanks for the help so far.

Thanks for the update!

Let us know how it goes.

It all works fine now. Had a problem with the modem staying online after 20mins (it kept disconnecting me randomly) - but that seems to have stopped being so consistent.

The only worry is that the new hard drive (60gb) is noiser..(!?!)

Any thoughts?