WPF: Improving Performance for Running on Older PCs

Are you applying any BitmapEffect-s to your UI elements?They are not handled by GPU, so CPU takes care of rendering them. If not used properly (e.g. having a OuterGlowBitmapEffect applied to a large complex element) they can have terrible impact on performance.

Also, you still might want to try profiling your app with a performance profiler. Just to see if it's not your code that causes this.

This is not normal for WPF - I'd suspect one of your developers has written code that runs a timer in the background (or more likely given your description, a mouse move handler) which is affecting the UI in some way.

If you have ANTS performance profiler (it's really nice) I'd run that over your app and reproduce the problem.

Once you've done that, ANTS should tell you fairly quickly what the problem is.If ANTS doesn't reveal anything at all, and shows you that in fact none of your code is running during this time, then I'd suspect buggy graphics card drivers.

You can test for this by disabling hardware acceleration by setting the following registry key, and trying again:

HKEY_CURRENT_USER\Software\Microsoft\Avalon.Graphics\DisableHWAcceleration to 1

Note: the DisableHWAcceleration value should be a DWORD