Your ram could be going bad, memtest is good for that
http://hcidesign.com/memtest/
Though a bootable floppy is best...
http://www.memtest.org/#downiso
Other then that, Do you happen to have nortons running? I remember way back in my dell days norton used to do something similar. Maybe try disabling any real time scanners you have on your pc (Does AVG/have real time???)
If that doesn't help then there's many other things that could be wrong, Would you mind posting specs of the pc?