This tip is for Visual Studio 2005. We have a new feature called the IDE Navigator. When Ctrl+Tab is bound to Window.NextDocumentWindowNav, the IDE Navigator will pop up, showing all available tool windows and files. You’ll need to hold down the Ctrl, kinda like Windows Alt+Tab dialog. If you have Stick keys enabled (Press shift key 5 times), you can just press Ctrl, then Tab, and the dialog will remain up.
If you do not like this new feature, and want the previous Ctrl+Tab behavior to just navigate to the next file, you can follow these steps to disable it. http://blogs.msdn.com/saraford/archive/2004/11/15/257962.aspx