Oblivion is one of the top "hogs" for system requirements. Do you know if your mother board requires AGP or PCI-E cards? Because AGP cards are becoming scarce and very expensive. Rick's ATI brand AGP card just fried this weekend; because it was top of the line when he bought it and because now it's scarce (because all mother boards are going PCI), to replace it with a brand new card would $800 (!!!!!).
Also, the beginning of next year, everything's going to change because of the release of Windows Vista, which will use DirectX 10 (which is not backwards compatible) as well as the new hard-wired copy protection for movie DVD playback.
/steps off geek soap box