my bad.........I assumed you simply wanted to make said machine "useful" and not necessarily into a gaming-capable machine.    Sorry about that, I shouldn't have assumed.  

What's the matter . . . don't they pay you enough scratch at Stardock?

He is stardock!

You know those Stardock guys, buncha bastards!

Honestly, it'd probably be cheaper to replace it-which I think you've been told more than once. 

With this board here you could do a fair change out to that model Dell you have. Plus buy a core2 duo processor with a good gt9800 physicalX graphics card and run your game very well. There will be issues of hooking up power and usb plugs for the front panel to this board. But for the price and what you have in mind this a value up grade for that case. XP pro x86 OEM would be good also and you can put 3 gigs of ram easily here. Power supply would have to support one 6 pin graphics card connection being usually 600 watt or better. Depending you can get away with less - like a 550 watt provided it has the plugs for an adapter to be used. I really do not like using any kind of AGP graphics cards. Seems there are always drivers that play funny with whatever you use.

Also this is a open box and you may need to have a few spare parts laying around to complete the install of the board. But some of that can be bought locally usually at a shop which does rebuilds and has a few things for leftovers for sale or as needed. All in all you would spend if you look around like $300 to $400  and have a pretty good updated system for most of todays OS and/or XP. Plus leaving it to where you could also improve a little down the road if needed.

Board

I like your project as it is though. It says a lot and gives others the true idea of what they can do if they want.