I can add that video memory size is also incorrectly detected in 32-bit Vista as well.
I have GF 7600GS with 256MB of video memory and AGP aperture in BIOS is set to 64MB.
No way i can have 551MB Vista SP1 shows me. It is shown in computer performance index tool, dxdiag and System Information tool.
And in CCCPI as well.