adding to my above reply.....
In case you wonder what this means ..... HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
It means .....
After you typed regedit in search box and pressed Enter, you will be in Registry Editor window.
Left column > There is an arrow head in front of HKEY_CURRENT_USER, click it ( it is termed ' expand ' ) So far understood ? OK, here goes ...
expand Internet Explorer
Now, look at the main box at the right > RIGHT click at FullScreen
click Modify > change no to Yes > click OK when done.