Pop-up window ‘ghosting’

Running WindowsXP on a Dell Precision WorkStation 690. I have an issue that started several months ago. Whenever I get an error ‘pop-up’ from one of the applications that I run, the pop-up window does NOT display the error but displays whatever was displayed on the desktop at the time of the generation of the pop-up. For example, if there was a Windows Explorer window open on the desktop at the time of the pop-up, a portion of the WinExplorer window comes up in the pop-up.

I have installed a NEW video card & uninstalled & re-installed the application; still same problem.

Any ideas?