A piece of a window remains on screen

On a Pentium III – (nothing has changed) computer running WinMe my client says: “When i go from one screen to another ( i guess thats how i would descibe it) it leaves a part of the previous screen ( aprox. 1 1/2″ x 2 1/2″ ) on the new screen. i candrag it and move it but the only way i can get rid of it is to restart the computer. as i am writting this e-mail i have a part of something i was looking up on the internet last night on the screen”.

Has anyone heard of a virus doing this or does he have a video problem? I will suggest he uses Ctrl Alt Del and look at tasks running to see if he got a virus program running. He does have and keeps Norton Antivirus up-to-date. Any other sugguestions?