MetroController allows you to disable Metro UI in Windows 8 without manual registry hacks or manual DLL renaming. MetroController does all dirty job for you.
It works only in Windows Developer Preview
It looks exactly like this:
There are two ways of tweaking are avaliable.First disables all new stuff in Windows 8, including Explorer's Ribbon.
Second option keeps Ribbon alive.
You can use this tool to rollback all changes.