A common reason if this messagem appear only when you try a particular game, can be that this game doesn't support this gfx.
My recomendation plan to solve this issue:
1. see in game box or with manufacture if your card is supported, if yes...
2. Run DxDiag.exe, by clicking on the Windows Start Button, selecting Run and entering "Dxdiag" in the open box and see if some DirectX features that is requeried by you game is disabled, i.e. DirectDraw, Direct3D or AGP Texture.