when you build a computer you build it, install windows\drivers\etc. and post it up on ebay.
you dont install windows\drivers, then use AIM, OC it a lil, browse the internet on it for a while and sell it as "New".
800$ tops
EDIT:
also if you put "Gaming Computer" in the title, ill have to punch you in the face, a 8300GS hardly qualifies as a "gaming card". not even nvidia thinks it is.