Configuring the Off Button
Q. When is an OFF button not an OFF button? A. When it's a Sleep/Hibernate/Do Nothing button. The standard setting for the Vista power button is the equivalent of the Vulcan Nerve Pinch - it gently puts the computer to sleep.. If you wish to change this default behaviour to something else, like a simple 'off' function, it takes a bit of drilling..

Go to Control Panel | Power Options. Under the checked 'Preferred Plan', click 'Change plan settings'. Under 'Change settings for the plan:..' click on 'Changed advanced power settings.' In the 'Power Options' popup box, expand 'Power buttons and lid' and 'Power button action'. Click on 'Setting' and in the ensuing drop down box, select the preferred action for the power button..

Finally, click OK and close the maladroitly-named 'Change settings for the plan:..' window.
Off you go now..