hello i have big big problem with my computer.
while playing computer games it crashes instantly freezing the image and sound.i have to restart the computer after 10 mins in order to work again.while browsing the internet the cpu usage jumps to 100% with no apparent reason. there is no process in the taskmannager(ctrl-alt-del) that uses the cpu.the computer starts working horribly slow at this point. i noticed while using a big fan pointing towards the open case of the comp a slight improwement(i must specify that the fan is a big one 30cm diameeeter used for cooling in hot summer days in offices) this is the only way i could get the computer to work properly. i must mention that i tested 3 video cards on the comp and there is no difference. i swaped and tested the memories with mem test. used a program to see what cpu motherboard or other temperatures and there was nothing wrong. i reinstalled windows 3 times and the problem was the same with all of em. i'm desperate pls help.

my system is a 3 ghz celeron with asrock 775i65pe motherboard, 1gb ram , gf6600 video.

i susspect it is a worm or a virus of some kind but i can't reach it

Do you perhaps get a blue screen?
If so this normally means RAM or a graphics card is at fault.

What graphics card are you currently using, and how much RAM do you have?
edit: ignore the above!
run an antivirus program
a hijack this log