You don't give any indication pointing to a possible cause nor any error message. That makes it impossible to answer your question. It could be anything.
Better post again at our windows7 forum http://forums.cnet.com/windows-7-forum/ and be sure to tell more than you did here.
I have Windows 7 Home premium edition. I can't seem to install Itunes 10.3. I've looked at several of the solutions on the Apple and Windows boards but nothing has worked. What could it be?