It should be a simple thing, but dear!, I coundn't find it. On Mac, you can use alt + 3. The combination is weird enough, but on windows 7, I couldn't type it at all, ... well until tonight.
Simply, it is right alt + 3. ##### hahaha.
To summarise all the key combinations
Hope this post helps you out of your frustration with Windows 7 on Mac bootcamp.