games crashing to desktop

this is a strange problem im having and i usually dont post asking for advice, but this has me stumped. the 2 games in question, c&c zero hour and bf2, keep crashing to desktop. might take 5 minutes might take half an hour but they will eventually crash with no error messages....they just quit.
now heres some things i have done to fix it:

downloaded drivers for my ati card/ran 2 different spyware tests (adaware and spybot)/ran 2 antivirus checks (panda and avg) /temperature of cpu is under 50c/ren reg mech.

and so far everything has come up clean

heres my specs

win xp
ati x800 pro
2 g ram
lots and lots of hd space

anyone any ideas?

 

Most of the time i see this it's when your anti-virus is running in the background so try to disable it and try your game i have the same problem with oblivion disable my A.V. problem fix.....

 

Yep have to agree, in fact if I'm not playing online I switch off Firewall, PestPatrol, AV, etc, etc. Essentially anything not needed to run my game and it frees up system memory for gaming.

When on the net notice how some times AVG just pops up and states "searching for updates" (or something to that effect) could be what your experiencing. I have NOD32 and can be a real pain in the arse for this, even after switching off?