tomshardware.com often has nice system builder articles for various budgets. In your case, have a look at this: http://www.tomshardware.com/reviews/gami...,3216.html
This is probably the best you can get with 500 bucks and has some good graphical muscles with that GeForce GTX 560 Ti to handle the likes of Skyrim.
I recommend going a 100 bucks over budget and getting a more decent CPU too, like the Core i3 2120 which is compatible with the same mainboard used in the 500 dollar system from the above link:
http://ncix.ca/products/?sku=59192&vpn=B...ture=Intel

Of course this is just the chassis and its internals! you gotta spend around 200 on a monitor and around 50 on peripherals.