wtf harddrive

ok if anyone could help me it would be much appreciated!

since a week or so i'm having these weird fps drops in ET. they only last a couple of miliseconds and occur every 2 or 3 seconds. as far as i know my pc is pretty clean, i formatted only a few weeks ago. it also effects my sound, like a stuttering sound together with the very short fps drop.

i've got an amd64 3400+ and a mid-range ati card running on winxp lite. it seems like it's either my hdd at work - logging or something or some cheap ass spyware. but i cleaned and checked, and i don't see any programs running on the background that shouldn't be there.

anyone else had this problem ? all I know is that ET is far from smooth this way

thanks !