It's not the computers that people don't like here, it's the dodgy cunsumer grade soundcards like the SBLive. For a computer, well, you can pretty much use anything decent (Mac or PC). But in the realm of digital audio, the golden rule is "the more the merrier". More CPU speed = more realtime procesing power for efects. More HDD space = can record more tracks per song etc.
There are some computer bits that are more useful than others (eg hard drives that are >= 7200rpm), so look around the older threads to see what's happening.
Just remember that you'll probably be on a reasonably frequent upgrade cycle for the machine, so the ability to upgrade your machine is important. This cuts out some of the name brand gear, cos they have no spare PCI slots or whatever. Look around here, and you'll see what people have said in regard to computer specs.
- gaffa