Dark Side:
On most computer monitors, if you turn the brightness control all the way up and the contrast all the way down, the screen will appear to be blank. Do this to your victim and they will drive themselves crazy trying to “fix” their “broken” monitor.

Open any application the victim might normally have open. Press "PrtScn" to capture the desktop as an image (make sure the mouse pointer and task bar can not be seen). Next, open an image editing program, and paste the image.

If the victim uses Microsoft Word, go into the victim’s computer and change the auto-correct feature so it misspells common words.

Take a Post-It note and place it over the eye of the victim’s optical mouse. When the victim tries to use his or her computer, the cursor won’t move.