(AMD + Vista Ultimate x64) + ATI/Nvidia drivers = fail

On 2 separate computers I am having the same problem.
1st PC is an custom AMD Opteron 170 with Nvidia 7900 GT
2nd Laptop is a DELL AMD Turion TL-50 with ATI Xpress 1150

I just bought the laptop 1 month ago and as soon as I opened the box I installed a fresh copy Vista x64. Upon idling at the login screen for 2 minutes the screen would shut off when on battery and upon moving the mouse, the screen would return with diagonal randomly colored lines moving across the screen preventing anything from being seen. The only way to fix it was to force shutdown.
The only way to fix this problem was to install the latest graphics drivers for ATI. It hasn't happened since.


Now, I recently upgraded my 1 year old PC to Vista and it doesn't appear to have the same problem with the Vista default drivers, but as soon as I installed the latest Nvidia drivers and even the Beta drivers, it does the exact same thing. As soon as I enter the password to login to windows, I have to do a hard reboot and go into safe mode to uninstall the drivers + delete drivers.
Here is a picture of what it looks like on my pc:


This is very frustrating. As I can't use any of the drivers from the Nvidia website to fix this. Anyone have any ideas?