Vista Aero Theme includes a transparent that really looks good. However, if you have a computer that has a underpowered video card you will experience a performance drop when the transparent effect is enabled. To speed up the performance of Windows Vista and still get the benefits of Aero, such as flip 3D and taskbar thumbnails just disable the transparency effect of effect.
Here’s how to disable Transparency
1. Right click anywhere on your desktop
2. Select Personalize
3. Open Window Color and Appearance and uncheck “Enable Transparency”