Windows uses software called "video drivers" to communicate with your computer's screen. If the video driver or its hardware aren't perfect, it can cause display problems, especially with software like PowerPoint, which really gives the display a good workout.
If you're having display problems, there's a Windows setting that can help you track down the cause of the problem and temporarily work around it. It's called Graphics Hardware Acceleration. Here's how you use it:
If you use Windows 95, 98, etc.
Choose Start, Settings, Control Panel
In Control Panel, doubleclick the System icon
Click the Performance tab
Click the Graphics button
Drag the Hardware Acceleration slider all the way to the left
Click OK as many times as needed to return to the desktop.
Restart the computer if necessary.
If you use Windows ME
Rightclick the Windows desktop and choose Properties
Click the Settings tab, then click Advanced
Click Performance
If you use Windows 2000 or XP
Rightclick the Windows desktop and choose Properties from the popup menu
Click the Settings tab and then click Advanced
In the next dialog box, click the Troubleshoot tab
Under Hardware acceleration, move the slider one notch to the left.
Click OK as many times as needed to return to the Desktop.
If you use Windows Vista
Rightclick the Windows desktop and choose Personalize.
Click "Display Settings".
In the Display Settings dialog box, click "Advanced Settings..."
On the resulting dialog box, click the "Troubleshoot" tab.
Click "Change Settings"
You'll probably see a User Account Control message box asking for permission to continue. Click "Continue"
On the resulting Display Adapter Troubleshooter dialog box, move the slider one notch to the left.
Click OK as many times as needed/close any windows that opened along the way, and return to the Windows desktop.
After changing acceleration, re-test
After setting the acceleration back, repeat whatever whatever caused the problem in the first place to see if it's now fixed.
You can either reduce the acceleration a notch at a time until the problem goes away, or move it all the way to the left, test, then if that cures it, try moving it to the right again until the problem recurs, then back off one notch.
If changing the video hardware acceleration solves the problem, it's a signal that your computer's video driver isn't quite perfect. Check with the manufacturer (of the video system or the computer) to see if updated drivers are available. Even if your PC is brand-new, it's probably been several weeks or months since it was built and video drivers change almost daily. (See below for more information on this).
Note that by default PowerPoint 2002 (XP), 2003 and 2007 do not use Hardware Graphics Acceleration in Slide Show view. This is by design, in order to minimize the chance of video hardware and driver errors. However, you or some other user may have enabled this feature. If you experience problems during slide shows, choose Slideshow, Set-Up Show and remove the checkmark next to "Use hardware graphics acceleration".