|Not sure why you posted this in the Vista forum.|
Set it to show all hidden files and folders - best left that way IMO.
"Temporarily" set to show protected system files too. This can make a few extra files and folders suddenly pop up - if so don't delete them.
You can now go through the Windows folder and see what is taking up all the space. There is no quick fix - you need to gather the info first. Get advice before going further (deleting files/folders can wreck the system).
Just for info my XP Windows folder is 8.6 GB but this will vary with what you have onboard.
Please come back and let us know how you got on.