Build it yourself. Go to www.newegg.com They have great customer service and they let their customers rate the products that they sell. You can get a good feel for what motherboards, etc perform well, and which ones do not. It's not hard to build a computer, and if you do build it, you will learn much about how to fix them when you have a problem. This might sound unimportant, but if you choose to upgrade/fix you will be very intimatly (not spelled right) acquainted with your pc. You could most likely save your case, cd/cdrw, floppy, etc.
Also, I have had good luck with IBM drives (I'd go with a setup that is about the fastest that I could afford. The more you save on things you already have and don't need to buy, the more you can spend for a faster computer (will be more in date for longer.......my desktop has been running for 3 years, and is still very stable and fast enough for my needs).