Windows Vista freezes

Hi,

Windows Vista freezes when the desktop starts showing up. Many times I had
to restart the computer from the button (it doesn't have a reset button),
then I have to do a System Restore so that I could work. Any solution?

Also, how can I disable that Shared System Memory? I bought a 256 MB PCI
Express Graphics Card to get those 224 MB shared between the RAM and the
internal Graphics Card, but still shows that those 224 MB are still shared.

My best regards.

PS: I already disabled that internal graphics card from the BIOS. The PCI
Express is the primary.