I must be crazy, but I recently decided to install Windows 2008 on the same physical server where I already have Vista Ultimate installed. The reason I did this was that I had an extra 500 GB drive on the server that was not being used, and I thought it would be a good place to install Windows 2008 so I could learn more about it. In addition, it was my goal to run several SQL Server instances in virtual machines in order to have several different SQL Server instances available for experimentation. Wow, I was in for a surprise. It can be done, but it is not explained very well anywhere I could find. Here's what I learned: 1) First, be sure that the drive you have available in install Windows 2008 on has already been setup and formatted from within Vista. In my case, this was drive E. This drive should be recently formatted and empty. 2) Next, you have to go through a convoluted procedure to prepare drive C of your Vista installation so that the Windows 2008 installation process understands that drive C exists. Apparently, Windows 2008 doesn't automatically know that it can use drive C for the initial installation process (temporary files) before the installation actually occurs on drive E. To find out about this process, see http://support.microsoft.com/kb/928232. 3) Once you have completed the above process, then reboot to Vista then startup the Windows 2008 installation program and following the instructions. Be sure that you specify the empty drive (drive E in my case) where you want to install Windows 2008. Once you are done installing Windows 2008, you can now dual boot between Vista and SQL Server 2008. Have fun!