Should be able to pick up a second hand job on ebay. Depends on your price of course but some good pcs for under 200. Last one i bought was originally about 1500 and got it for 400. Great little thing.
One before that was 40 quid.
Look for a lot of ram, and decent processor.
4gb bare min, but better with a bit more.

Also 64 bit with a pro windows licence are better than 32bit home versions