I played this one when I was in grade 7 or 8.
We were in the computer labs, and at one point I switched the keyboards around for mine and the person beside me. So she came back, and tried to type into wordpad, and it wasn’t working. She was starting to get frustrated, when I started typing “STOP POUNDING ON ME!!!! IT HURTS!!!!”
Seriously freaked her out. Of course, she brought a teacher over. And I ended up getting in trouble. But it was fun while it lasted.
When dealing with noobs in multiplayer games, people would sometimes tell them to press Alt+F4.
On school computers (and sometimes my mother’s, to her dismay), I would go into the task manager, go to Processes, and kill the “explorer.exe” process. It makes the taskbar and icons disappear.
However, you can put it back by going to the task manager again, going to File >> New Task (Run), and opening explorer.exe back up. 
Rebooting the computer also puts it back.
This thing is great for pranks — I occasionally send emails to friends making it look like they emailed themselves. It’s for use for mischief, not malice — and I don’t recommend sending one to your straight-laced boss!
This is pretty neat — it is for Macintoshes and uses the accelerometer* to make the desktop “fall down”!
Despite it being called a “virus”, it’s actually just a harmless gag.
Tech Support: Hello?
Customer: My desktop just collapsed!
Tech Support: …..
* The accelerometer is only MacBook Pro, I think. It shuts down the hard drive when the computer falls, to prevent damage.
Here is a blog post with several classic computer jokes.
For all you geeky people out there, this will be old. But if you’re new to this, it’s great to play on co-workers or family members. My mother was not too pleased.
I don’t recommend doing this if your victim is bigger and stronger than you.
First, you take a screenshot of their desktop, and save it. (For more realism, you can even put a program into the screenshot.)
Then you hide all the icons (you can either go into properties to hide them, or put them in a folder in My Documents. Deleting them is not such a good idea. (I learned this by accident.)
Next, you put up the screenshot as their desktop. If you want even more fun, hide their taskbar. Then leave their computer and try to look innocent.
Lots of people will try rebooting several times before realizing.
