PC's are way too loud. Their hard disks grind, their fans whine, and their cases clatter. Bothersome? Yes. Insurmountable? No way. You can reduce the noise with a few simple tweaks. First, turn your PC off, remove the case cover, turn the system back on, and use a car mechanic's stethoscope, or just a paper-towel tube--to isolate the noise source (don't forget to turn your PC off and put the case cover back on when you're done).
If your hard drive chatters, make sure the screws attaching it to the PC case are tight, and examine the bracket holding the drive to confirm that it's tightly connected to the PC. Check the gap around the case cover for vibrations; if you detect any, wedge in a piece of cardboard or use sealing foam. If you're careful, you can lubricate the cooling fans by removing the sticker covering the lube hole and dripping one drop of oil into the hole. Wipe off any excess oil and then either reapply the sticker or replace it with tape.