Locked out of PC

[Harrison]

That is true. Faulty ram can start created very random crashes. Equally a dying harddrive can cause system file corruption which can BSOD the system randomly.

I good way to test both is to download a free CD image called the Ultimate Boot CD. This contains the memtest utility and utilities to test all makes of HD. It also has loads of other useful tools and utilities on the disc and is worth having for emergencies.

You can download it from http://www.ultimatebootcd.com

[TiredOfLife]

Cheers all, some good advice above.
Have persevered as I am a glutton for punishment.
The BSOD seems to kick in whilst AOL is trying to sort itself out.
Have managed to get the latest version of Avast, Spybot and Adaware installed using various combinations of different safe modes and user accounts.
Earlier version of Avast wouldn't install and neither would AVG antivirus and AVG antispyware.
The machine is absolutely riddled with viri.
Already tried a Windows repair with a CD I had, but will try this again once Avast has finished.

[Harrison]

Doesn't sound good if the system is riddled with viri, as you say. If that is the case then the only solution is a format and clean install.