this is an easy prank you can do to a friend that loves his computer... say hes in the bathroom for 15 seconds??
Step 1: First...
first you want to bring up task manager
do this by pressing control+alt+delete
Step 2: Second...
click the "processes" tab, and find explorer.exe
and then, press "end process"
NOTE: be sure EVERYTHING is minimized or else it wont work, all the icons and the start menu bar go away but programs that are still up
Step 3: Then
when you think your friend has had enough, bring up task manager again, (control+alt+delete),then click File > New task (run)
then type in "explorer"
and everything should come back up