I've had several PC based set ups, all had problems of sorts!
Bought an old Mac G5 for about £300 (dual 1.8 ghz, 4 gig RAM, two 500 gig HD's) then a used Digi 002 (I like hands on approach, beats using a mouse on faders) and finally a copy of Pro tools LE8 when it came out. The whole lot cost about £800
I already had a pair of Tannoy reveals and a BIG monitor (would prefer dual monitors though)
It runs without fault, has done for two years!
The only time it screws up is if I run a demo of a processor hungry plug in with a track with lots of tracks, but that is down to the G5 being fairly old now. I could spend a few more £'s and get another used machine that would hamndle more, but i just dont need it!
Tony