MS word 200 won't completely open/run on my Vista system

I have MS Word 2000 version on Vista system. MS Word has been running fine. However, recently MS Word won't open completely. Sometimes it only half opens (that is it runs, but only half of the screen appears), other times it fully opens, but there is no cursor, and it won't respond to any mouse clicks. I have run numerous virus checks, and have completely uninstalled and reinstalled MS Word. Nothing fixes the problem.