Partial Upgrade [YEA BABY]

I'm going to try and talk my dad into buying me some pieces for my new computer. I had two sticks of memory in my computer - 512 and 128. The 128 crapped out on me (after Windows started messing up bigtime and wouldn't boot even in safemode). The USB and PS/2 ports have long since burned out on the motherboard... and now I'm using a USB add-in card to plug in my USB devices. The video card is starting to die and is giving me some crazy visual video errors, such as huge blobs of multicolored lines across the screen (and its not the monitor just got a new one).

Anyway, I'm concerned the motherboard and video card are doomed. The case I have is ATX formfactor - so if its at all possible I'd like to stick with that yet upgrade the motherboard, memory, CPU and video card. The sound card I have, case, keyboard/mouse, speakers, NIC card, etc are fine. that way it won't cost me a fortune and hopefully I can use my own money to buy some new cosmetic stuff for the computer: new fans, fan controller, etc.

What would you suggest I upgrade into. Budget may or may not be a limit, so lets say... nothing above 500-700. Doesn't have to be the latest and greatest. and AMD too, with room to OC. Thanks!

So you just need cpu/vid/mobo/ram pretty much?

Get a stick of 512mb pc3200 buffalo tech (winbond chips) for like 85 bucks, something like an asus a7n8x or abit nf7 gonna cost you ~100 bucks. Radeon 9600pro 128mb are about 150 bucks on the net, and an AMD AthlonXP 2500+ barton will set you back 90 bucks. All that comes out to around $425 and will last you quite a bit of time and will play all the games out atm and coming out very nicely. And if your budget is 500-700 gives you some extra cash for the fans, fan controller, etc :P