I finally got a chance to try the keyboard shutdown command on a Vista operating system. I found that I had to go one more step - I had to click on "Enter". So it went like this:
Windows Key then
press right arrow 3 times
then press Enter
I don't know if there are variations from on Vista to another. You might want to try this to see if it works on your computer before writing it down and storing it away.
Here's hoping you never need it! :-)