My videocard that bad?

Ey, guys

Although I've got a video card with a relatively high VRAM (1024MB). I am experiencing low FPS in games like Area 51 (which requires 128MB) en NFS Undercover (which requires 256MB). Anyone would think that I could play these games at pretty high quality, but no. I set the video settings of NFS Undercover to the lowest possible and still there's no increase in performance... These are also pretty old games, so I'd expect those games to run smoothly... Does anyone have any explanation for that?

If it helps:
My videocard is an ATI Radeon Sapphire HD 4600 series AGP (1024MB), my videocard drivers are up-to-date and I've got the latest version of Direct X...