The “Shut Down” button in Windows 7 can be customized
with another action, if you use shut down action very
rarely, but you more often restart it or put it on hibernate.
To change the action of shutdown button, Right click the Start Button,
go to Properties and choose the 'Power Boot Action' to do whatever you want,
from the given options. It will give you a drop down list amongst following
option to select from.
1. Switch user
2. Log off
Now the button at Start Menu would change and perform the action as selected.