My son just uninstalled Vista and went back to XP as he wants to run games on high settings but they run so badly...and he has 3.2 dual core, 2gigs of ram and geforce 8800 XXX card!
With XP he can now run everything on full settings.
You often get much better spec PCs for the price from the net so stop looking in the big stores and see if someone here can give you a link.
maybe like this: http://www.evertek.com/
Forget all the extras stores throw in like a great sounding mouse or wireless keyboard, free software or printer, you can buy these extras anytime for a few $s so spend as much as you can afford on a decent spec PC and it will last you years (especially if you upgrade the RAM and graphics card) rather than having to buy yet another one in 18months - 2 years!
You could just buy a base unit off the net and a monitor instore or preowned if you see a special deal.