256 MB card recognized as 64 MB

A recently installed Radeon 9550, 256 MB, video card shows up as the Radeon 7000 series 64 MB it replaced. All drivers were removed and the new card installed but no matter what I do, windows will not recognize the card. I fear that the AGP Card on this 1.3 GHZ system will not support the 4X / 8X video card. I am puzzled. Any suggestions? Thnx…