Well, if I'd thought about it sooner I'd have put this up as a sort of last minute christmas shopping thing but...it's too late.  Still worthy of note.  It's just remarkable how cheap it is to upgrade a PC now with all the price drops in DRAM, CPUs and GPUs.

For instance, getting a 2.5ghz Intel E5200 CPU (or a cheaper 2.2ghz Intel E2200 CPU to shave off $20 bucks) OR a cheap ASRock intel motherboard or if you're an AMD fan, an Athlon X2 5000+ and a cheap ASRock AMD motherboard

plus 2gig of RAM (4gig of RAM isn't really very useful yet)

And finally a Radeon4650 video card (or a 4670 for just $15 more) 

 ...you're looking at an upgrade that can get your PC to play any modern PC game for just a bit over $200 (assuming your hard drive is large enough).  The ASRock boards use the older 20pin ATX conectorsand the Radeon 4600 series don't require an external power supply SO even older supplies should be able to deal with it as long as they're rated at 300 watts or higher.