Well that's ok. First off your going to want a decent enough graphics card, on your budget i'd suggest a 256mb Geforce 6600GT.
The proccessor, Well an overclocked AMD 64 3000+ will do just fine and it's not too expensive, 'important' make sure you have a good CPU fan/heatsink no matter what.
You'll need some RAM, I'd reccomend 1GB, if you can afford it maybe 1.5GB, Make sure it matches your motherboard, and go for makes such as kingston or Corsair.
I'm no expert on motherboards, just make sure it's not cheap and make sure your RAM is compatible and that the amount of pins on your proccessor 939 or 754 matches the amount on the board, same goes for the power supply which should be around 500w and NOT a cheap one, aim to spend about $40 on it, you won't regret it, thermaltake is a good brand to go for.
Hope this helps for now