PC Crashing - Overheat, memory or Infected??

[Oggin Aviator]

Hi all

My PC at home keeps crashing, especially when running SpyBot, Adaware and routine antivirus scans. I am going to to try and run a Hijack This (1.99) scan tonight, however have heard that the Ms4Hd parasite will crash HijackThis when it reaches the new O23 (NT Services) section. This parasite deliberately crashes most apps that query any regkeys/files it owns. If this is the case tonight, I will try a copy of HJT 1.98.2 (which shouldn't crash with Ms4Hd). Assuming HJT works I'll post the log here later.

If Ms4Hd is the culprit, does anyone know how to get rid of it?

In the meantime, could it just be overheating or memory - it has been stable for about a year however following some advice on another post I tried to run memtest yesterday and all I got was a page of blinking sets of 4 characters during boot up from floppy.

Any Ideas?? Any thoughts appreciated.

Oggin

p.s.
3.2 Athlon
1 Gig RAM (2 pieces)
Win XP Pro SP 2 with updates
Hardware Firewall (Router)
Software Firewall (McAffee)
McAffee Antivirus etc.
IE6

p.p.s. Edit to say when it crashes I get a blue screen of death, sometimes it flashes up and is disappears too quickly to read, sometimes I have enough time to read an "IRQ not less than zero" error prompt which leads me to think the memory is on its way out. I am not, however, sufficiently knowledgeable to know what to do about it! Hence this post. Cheers.