You don't actually change to a different OS. You change the compatibility mode. Right click on the game icon or the game .exe file, click on Properties and click on the Compatibility tab. Select the operating system that works the best.
An alternative method is to go to the Compatibility Wizard. Start > All Programs > Accessories > Program Compatibility Wizard. The advantage of the Wizard is that you can try running the game in various modes within the Wizard program until you find the one that works best, then select it and exit. Saves some time over the first method.