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.