In the recent months, the amount of criticism that both NVIDIA and ATI received for their respective multi-GPU concepts was just unbearable for their poor press release folks, the wee lambs. As it turned out, NVIDIA and ATI were not the only guilty parties in the whole case, but Windows Vista was implicated, too. Microsoft just posted an update for both 32-bit and 64-bit versions, fixing issues where operating system would not pass instructions for the 2nd GPU to the driver, meaning SLI and CrossFire would effectively work as a single chip cards. So, NVIDIA and AMD could have done whatever they liked, and their dual GPU systems would just not work. - The Inquirer

Microsoft fixes SLI and CrossFire with Windows Vista

If you're running SLI or CrossFire system and Windows Vista, you should not think twice about this one... Windows Vista, a delayed operating system nightmares are created of. So before you continue and try to find out the issue of low performance with you multiple graphics cards, just go to the Microsoft website and download the hotfix available. In the end both NVIDIA and ATI received quite some critics, while it required a fix by Microsoft on their new Vista operating system. Let's just hope that Microsoft has learned a lesson, and takes up their role for correct and valid support for multi-GPU systems.