So every now and then i hear this engine-like buzzing coming from my pc. i have no clue what it is, but I just whack the pc on the head and that usually fixes it right there. but it still comes back every now and then when I boot up. Any thoughts?
It is probably a fan vibrating or a cable contacting a fan blade. There are only a couple of moving things in a PC. Fans and disk drives. Disk drives spin at higher RPM so they can vibrate. You can use rubber mounting systems to eliminate that noise. Fans are the same. You can use isolation techniques to prevent them from vibrating. I have some cases where chaning the tightness of the screws holding the side panel will stop vibrating noise.