Er...can't you just open up your case and listen?
The only moving parts in a computer are your system fans and disk drives. Fans are generally noisy if they are either dirty, or if they are...spinning fast...which is a good thing I suppose.
Vibration control may be something you may want to look into, putting rubber washers between your case and moving parts to stiffle vibration
Intel C2D E6320 / AMD Athlon X2 3800+
Gigabyte 965P DS3 / DFI nF4 Ultra-D
2GB OCZ Gold PC2-6400 / 2GB OCZ Gold PC4000
eVGA 8800GTS 320MB / eVGA 6800GS 256MB
150GB Raptor / 74GB Raptor
2x500GB / 320GB
OCZ GameXStreme 850w / OCZ StealthXStream 600w