My system specs are:

p4 3ghz HT oc'd to 3.2ghz
Intel 875 mobo
1GB RaM
128mb 9800 pro at time of render, now a 256mb 6800gt oc
2x36gb WD Raptor RAID 0


I work at best buy and have seen some excellent spec's on computers they sell for relatively cheap. If you computer is slow and you don't exactly know how to build one. They have a dual core rig with 1gb ram and 250gb HD for 850.00 only draw back if the video card you would have to put one in being that it has integrated.