According to the Oblivion website you need to have an ATI X800
series, Nvidia GeForce 6800 series, or higher video card.
Here is a list of supported video card chipsets. However you can
still get the game to work if your card is not listed here.
* ATI X1900 series * ATI X1800 series * ATI X1600 series * ATI
X1300 series * ATI X850 series * ATI x800 series * ATI x700 series
* ATI x600 series * ATI Radeon 9800 series * ATI Radeon 9700 series
* ATI Radeon 9600 series * ATI Radeon 9500 series * NVIDIA GeForce
7800 series * NVIDIA GeForce 6800 series * NVIDIA GeForce 6600
series * NVIDIA GeForce 6200 series * NVIDIA GeForce FX series