When you shutdown your Windows 7 computer using the power button, a shut down dialog box is opened listing the unsaved works and the processes preventing Windows from shutting down. You may select to force the shutdown or you can click on Cancel.

If you click on Cancel and then go back to save all your works, THEN THE NEXT time you try to shutdown your computer, it WILL take considerably more longer to shut down.


KB2719667 offers an interesting explanation:

If an application is preventing Windows from shutting down (ex. unsaved work), Windows will wait a period of 60 seconds at the force shut down dialog before forcing the application to close so shut down can continue. If the user cancels out of the force shutdown dialog, Windows still retains the 60 second timeout value. As a result, the next time a shut down occurs, even if there are no blocking applications, shut down will be delayed until the timeout value expires.

This behavior only occurs when configuring the power button to shut down the machine. When shutting down Windows through the Start Menu, the problem does not occur as the timeout value is not retained when cancelling out of the forced shutdown dialog.