Just started happening regularly at the end of last week. User is in Outlook and clicks on something behind Outlook and part of the background or background app becomes merged with the outlook window - doesnt come cleanly to the fore so that it can be used properly. Then if you try to drag it away to one side it leaves traces of itself as you drag. RAM is 3Gb and approx 2 gig available and processor usage seems unaffected. Could it be as simple as an Office reinstallation? Or a complete format?