i had a windoze tower i built a year ago and it made noise constantly... it drove me nuts. i finally discovered that if i went to the sound panel and muted "CD Audio" the sound would stop. cant figure out why exactly it worked... but it got rid of all the backround noise, and in addition i could still play cds. in fact i have that comp still and if i uncheck the box i still get weird sounds... my guess is maybe if you open up your tower and check the cable goin from the cd drive to the motherboard (or sound card) and check to see if its "clean" - no rips or anything... check also if its plugged in right. if its bad you can replace it at like frys or somethin... worth a look