Hello All!
I've been away from the Linux community for a while, but I thought you guys might be able to help me out with something.

When I boot my computer, it's relatively quiet, but at some point during boot, it begins to emit a high pitched buzzing of sorts. In Linux, it starts when X shows the nVidia logo. (I'm Running Ubuntu 5.10 with the better nVidia drivers.) When I boot XP, it used to start right at the welcome screen. It seems like it may be starting a bit earlier now. I don't know if it could be a fan or hard drive or something, but I'm pretty sure it's not a CD-ROM drive (I've disconnected my 2, and it didn't fix the problem.)I've tried switching out my video card for another, and I don't believe the noise stopped.

Possible Clues:
-When I boot Knoppix off a CD, there is no noise.
-When I use Abit uGuru to overclock my system in XP (specifically processor speed), the pitch of the noise changes.

Does anyone have any suggestions of what it is or might be?

Here's my hardware list:
Antec P180 Case with 500W SmartPower PSU
Abit AV8 Motherboard
AMD Athlon 64 3500+ (Newcastle Core) with Stock heatsink/fan combo
2 Western Digital Hard Drives. 120GB and 30GB, 7200RPM
eVGA nVidia Geforce 6800 (AGP)
ADMtek AN983 10/100 Ethernet Adapter

Thanks!