The Aero feature is definitely makes Vista an attractive operating system it also places a heavy burden on your PC's video system. So, disabling Aero should be the first step to help those systems which are struggling with Vista.
Right Click on the Desktop, scroll down and click on Personalize
The
Personalize appearance and sounds box will pop up. From there, click on
Windows Color and Appearance.

Click on the link at
Open classic appearance properties for more color options (see arrow)

The way to turn Aero off is by selecting something else. In this case, select
Windows Vista Basic. If your longing for the past, you can pick
Windows Standard or
Windows Classic versions.
Once you've made your selection, click
Apply and then click
OK
Keep in mind, if you have the Starter or Home Basic version of Vista, Aero isn't available.