Windows logo key+L locks the keyboard and mouse.
Ever wanted to lock the keyboard so your kids can't mess things up when you leave the room!.
I've been looking for a solution to this problem for some time as my 18 month old son cant keep his little fingers off my keyboard or the mouse.
Basically what happens is when I leave the room say to make a coffee he rushes over and messes around presing keys moving the mouse etc., when I come back I find he's either restarted the machine or quit out of the program I was using at the time, thus losing any work I might of been doing (AAARH!).
But!, not anymore just hold down the windows logo key and press L and it will take you straight to the logon screen, then it doesn't matter what anyone presses unless the know the password.