I've built PCs but I've never had to replace the hardware on my mac (thanks to good quality parts) and I want to pimp out my G4 tower. I'm interested in purchasing some cool blue or red LCD fans for it, but I was wondering if I can just walk into a Comp USA and find a..let's say a fan for an ATX form factor, and plug it right into my Mac? Or do Macs have their own set of form factors? Thanks.