You can, you just have to do so from the command line.

First open a command prompt window (If on Vista or Windows 7 make sure to run the command prompt as admin).

Next type: Shutdown -r

The "-r" means restart.

Add -t 00 for no delay.

You may also save this as a shortcut on the desktop, start, or taskbar by setting the shortcut's target field to: C:\Windows\System32\shutdown.exe -r -t 00

That's it. The machine will now restart. Of course you'll lose your connnection to it and have to remote in again.