He's using Win ME (I know, I know). When he tries to do anything, open Word, use the internet etc, the computer freezes and takes about 5 minutes to open any window or do anything.
At first we thought it might be a virus or spyware (Limewire user).
I've posted a HJT log here
However, whilst waiting for a response, I've downloaded the IBM HD utility (it's a Dell, checked the HD) and every time I try to run it the computer shuts down immediately after loading the 2nd floppy disk, when it's about to check the drive. I hear the HD kick into action, that little click you hear, then the computer immediately reboots.