If your video card is not fast enough to handle Aero on Vista, one trick you can try is disabling certain elements of Aero. This allows you to keep some of the benefits of Aero while not killing your computer. The two elements of Aero that are easy to disable and that help speed things up are the transparency and the animation effects.

To disable transparency right click an empty area on your desktop and choose Personalize from the menu. In the right part of the window that opens, select Windows Color and Appearance. On this page there is a checkbox next to Enable transparency. Uncheck this box and the transparency will be disabled.

If this doesn't speed things up enough, the next thing to try is disabling of the animation effects that occur when you minimize or maximize windows. Right-click on your Computer icon and select Properties. Choose the Advanced system settings from the left side of the window. In the Performance section, click on the Settings button. Select the Visual Effects tab and then uncheck the box next to Animate windows when minimizing and maximizing.

This should help speed up Aero while not completely disabling it. If it's still to slow, work your way back to the Visual Effects panel as there are many other effects there that you can turn off until you get Aero performance that you find acceptable.