I have had a NVidia 6600GT AGP graphics card since January this year.
In April I formatted the computer because of frequent crashes and shortly after noticed that the graphics on Medal of Honor Pacific Assault were very distorted as in there were lots of missing polygons. As I was only playing on Call of Duty, which ran perfect, I chose to ignore the problem.
I've just installed the Battlefield 2 demo today and when I went to play, exactly the same problem that I had on Medal of Honor appeared.
No as all products ship with a 12 month warrenty, although as you bought it off ebuyer it could prove to be a bit of a headache sending it back as they aren't the quickest of suppliers, just a thought have you an other card to test that the agp slot is not knackard.
Reason I ask is the artefacts in the graphics you posted seem common to a card being pushed too hard in overclocking terms, the 6600 gt (128mb model) should have stock speed of 500Mhz for the core and the same for memory, the best way to check is to download rivatuner and see what speeds the card is running at and compare that with the stock speeds for your card. You can get rivatuner from click here
possibly underclocked ?? there's something amiss with that speed, make sure you compare the speed with the stock speed from YOUR manufacturer as different manufacturers sometimes change speeds a little for the same card