You could check out www.micropro.com and build your own system or buy a preconfigured one.
You should buy a dual motherboard and if cost is an issue get a second proc later but get the fastest single proc you can afford.
You need to have at least 512mb of ram.
Then get a large IDE hardrive
CDR drive Sound card if the motherboard doesn't have one.
There are lots of inexpensive video cards.. you really don't need to spend more than $350 on a video card to get decent results.
I have several Tyan boards and they have not let me down.. other people seem to prefer ASUS or MSI motherboards.