Step 1. Right Click on your desktop and choose "New->Shortcut".
Step 2. In the box that says "Type the location of the shortcut", type in "shutdown -s -t 3600" with out the quotation marks and click next. Note: 3600 are the amount of seconds before your computer shuts down. So, 60secs*60mins=3600secs.
Step 3. Make up a name for the shortcut and you're done. You can change the icon by right clicking->properities->change icon-> browse.
More Info: -To make an abort key to stop the shutdown timer just create another shortcut and make the "location of the shortcut" to "shutdown -a" without the quotes.