Hey all, this is my first post so here goes.

If you have windows vista and you have installed the ATI Drivers for either xp or vista beta drivers and you are getting the Ati2dvag.dll bsod and reboot on shutdown, or Error 43 in the device manager when it finds and installs your graphice card here is a fix that should stop that from happening.
Remove all ati drivers, and use driver cleaner professional 1.5 to make sure all ati drivers are gone.
Reboot pc and enter your bios.
Find AGP Aperture Size and Change to 256mb, Save changes and restart.
Reboot back into windows vista and it should find your video card and load drivers supplied by microsoft.
Reboot pc and check in device manager that it has detected your card.
Change resolution to what ever suits you.
That should be it now, your pc should be able to shutdown with out bsod or error messages related to graphics.

Have tested on RTM Release of vista. PC P4 2.8ghz, 3gig ddr400, 3 * 250gb hdds, Sapphire Radeon x1600 256mb AGP, Windows Vista Ultimate.
Installed and ran Counter strike source - High Quality, Widescreen 16:9 - 1680 * 1050. Min frame rate was 40fps using Fraps 2.8.2.

Enjoy Parrey