my pc is locking up...help please

so heres the scenario. i am browsing, and say i want to play a song on wmp or open 'my computer'. well sometimes when i try to open my computer the whole thing just locks up....ill get that little flashlight icon or whatever it is like its looking for something, then it will just stop responding. ill then gert that box telling me i have encoutered an error and wether or not i want to send or cancel. so when i hit cancel, all the icons dissapear from the desktop and then come back again after say 10 secs.
this happens all the time with different programs....they just lock up and stop responding.
ok here are the courses of action ive taken....ran trend micro-no virus
ran avg-no virus
adaware, spybot sd, yahhoo anti spy-nothing serious
reseated my heat sink in case of overheating and put a fresh coat of that coolent stuff on the cpu. this brought the cpu temp down to 35c but im still having the same problem
ok here are my system specs.
win xp
amd athlon 3200+
2x512 ram
160gb hard drives
ati 9600 pro

im thinking the ram is failing....if so how do i check this?
thanks in advance guys!!

 

You're running both AVG and Trend Micro antivirus. Running two antivirus programs on your system is a no-no. It appears that there are problems with Trend antivirus, as evidenced by this article just published today:
http://msn.pcworld.com/news/article/0,aid,120560,00.asp

Try uninstalling Trend and AVG and reinstalling AVG or Avast...