Its most likely created by the cdrom stopping, then having to spin back up. Some cdroms have the timeout (due to inactivity) set at a rediculously low time, like 15-30 secs. An ideal drive will spin at high speed for about 1-2 mins then reduce to maybe 2-4x speed for another 5 mins before stopping. You can sometimes get programs/driver addons that can adjust this (for good drives that is). Also maybe try adjusting the CDrom cache size or getting a CDrom cache program, that way the cache will keep the data stream going until the drive spins back up.
 
It could also be things such as network timeouts and IDE controller timeout errors caused by small device errors and also the power management settings. Check to see whether your PC is trying to put the Harddrives to sleep, or check in the event veiwer for error messages (in administrative tools).
 
Good Luck!

Thanks for the suggestion, but one of the games i was having the problem with was the Thief 2 demo, which i was running entirely off the dard disk, which, if i'm not mistaken eliminates the CD-rom theory..
 
This generates no events. i would have thought that if it was a hard drive spinup delay i would have been able to hear the noise the drive makes while spinning up..