The default setting in the Windows 7 start menu power button displays Shutdown action. But should you wish to, you can change what the Power Button does from Shutdown, to Switch User, Log off, Lock, Restart, Sleep or Hibernate in Windows 7.
Power Button action and settings
You may depending on your usage, change its default action to:
– Switch User
– Log off
To do so, right-click on Taskbar and select Properties. Once this box is open, select the Start Menu tab. Here under Power button action, open the Drop down menu, and from the options available, select action. Once this is done, click on Apply > OK.
You can also do it the following way. Open Control Panel and choose Power Options. Next, click on ‘Change when the computer sleeps’ link.
Then, click on ‘Change Advanced Power Settings’ link.
Scroll down the list in the window till you find ‘Power Buttons and lid’ > Change the default action of the Start Menu Power Button, by expanding its view.
Hope it helps!
Also, see this post on Change what the Computer Power Button does in Windows 10/8/7.