Maybe some help here:
http://windows.microsoft.com/en-US/windows-vista/Turn-off-a-computer-frequently-asked-questions Can I change what happens when I click the Power button on my computer?By default, Windows puts your computer to sleep when you click the Power button. However, you can change the default setting so that clicking the button causes your computer to sleep, hibernate, or shut down. (Any changes you make will also apply to the physical power button on the computer itself.) To change the default setting:
Open Power Options by clicking the Start button Picture of the Start button, clicking Control Panel, clicking System and Maintenance, and then clicking Power Options.
On the Select a power plan page, click Change plan settings under the selected plan.
On the Change settings for the plan page, click Change advanced power settings.
On the Advanced settings tab, expand Power buttons and lid, expand Start menu power button, and then do one of the following:
If you are using a mobile PC, click On battery or Plugged in (or both), click the arrow, and then click Sleep, Hibernate, or Shut Down.
If you are using a desktop computer, click Setting, click the arrow, and then click Sleep, Hibernate, or Shut Down.
Click OK, and then click Save changes.
