>I'm trying to confirm that x64 allows the video memory to be mapped up out of the RAM range. My notebook has a 1Gb video card and all 4Mb RAM seems to be available for my own use using Vista 64.

Yes, on x64 the memory area is mapped into the address range beyond 4 GB. You definitely have all 4 GB available in 64 bit mode. My laptop is a dual boot system with 32 bit and 64 bit Vista which works just fine fore me as I work in VMs anyway. In 64 bit mode I do have more memory available. However, the system needs about the same amount of memory more than the 32 bit version. In the end I didn't gain anything and ended up using mostly the 32 bit version. Less issues with USB drivers, this way.