Not worth spending any money on when you can get a quad core CPU and AM3 compatible motherboard for about $150. You can basically build a whole new (modern) system around that for $400-$500.
Not that your old machine is COMPLETELY dead ... you could theoretically drop in an old dual core for $50 or less, which would let you support a video card in the $80-$100 range. While you're at it, adding another 1GB of DDR-400 would be a wise idea, and run you about $30.
Basically, I would only do that if you want to keep it as your second computer, though. Or if you're completely broke. It'll still be barely passable for modern gaming.
Same as your other post, no. It's 939. It could do some basic gaming, but not a whole lot of current apps. Really, just make it a NAS. That baby would be stuffed with so many movies if it was in my house...