im building a new pc this weekend and im going to try out an ati card for the first time and been reading on the hd stuff this is the card im going to get

ATI RADEON HD3870 Graphics Card

my pc specs this weekend will be athlon dual core 64 4800+
2 gig pc 5300 ram that video card and a nice hard drive.

my question is does it convert the game feed into hd or does the game have to support it and is anyone running the game on this kind of card who can give me some info as to how well it runs currently im running athlon 3500+ 1 gig ddr with 8600 gt oc so im hoping its a big step up