Using
multiple displays with
Windows Vista is slightly different from using multiple displays with Windows XP, although most of the functionality is exactly the same as it was with XP. In Windows XP, different video cards from different manufacturers could all be installed on the same system. For example, you could install a high-end graphics card from one manufacturer in the primary
PCI Express slot and then get a low-end card from a different manufacturer to power peripheral displays. Although these two different cards would be using two different display drivers (a piece of software that tells Windows how to use the graphics card,) this configuration would normally work under Windows XP.
However, Microsoft claims that having multiple VGA drivers under Windows XP often causes stability issues. In order to resolve this issue, Windows Vista requires that all installed graphics cards use the same display driver in order to run the
Aero 3D interface. The consequence of this change is that all graphics cards installed on a single system should be from the same manufacturer. For example, Nvidia cards should be paired with other
Nvidia cards,
ATI with other ATI, etc.
If you would like to use multiple
VGA drivers under Windows Vista, Microsoft claims that you can force Vista to use a legacy XP driver (XPDM driver) with your graphics hardware. However, under this configuration you would not be able to use the Aero 3D interface.
One enhancement in Windows Vista is that the
remote desktop client is now
multi monitor aware. If you are using multiple displays and a technician or a co-worker needs to remotely access your computer using the remote desktop feature, your entire desktop will be viewable to that person even if he or she only has one display.
If you are buying a new system for use with Windows Vista, make sure that all of the graphics cards that are going into the system come from the same manufacturer.
Reference:
Microsoft: Multiple Monitors on Vista 
