Unwanted window appears when Word starte

An odd thing happens when one of my clients opens Word 2000. The normal blank document editing window opens, followed by an second (document?) window without an editing area, and which can't be closed. After several tries, he is eventually able to switch to the editing window, but the other one reappears when he tries to do something simple, like a text search. It's like a badly-behaving debug window. Has anyone seen this and found a resolution? Uninstall/re-install has been tried.

Thanks
Jim