A simple but quick and always amusing prank is putting the screen rotation hotkeys to uses Microsoft never intended. Just run by a co-worker’s desk, reach over and hit Ctrl-Alt-up or down to rotate their monitor orientation. If you have some alone time, you can one-up it by also going into the Control Panel and setting their mouse to left-handed. They’ll spend 10 minutes with their head tilted sideways trying to figure out what the hell is going on.

Since you’re already under the desk, try out another switcheroo: the speaker swap. Just plug their speakers into your computer. Now start playing something like a low-frequency heartbeat sound on loop and see how long they try to stop the nuisance on their computer. For a more powerful variation, don’t switch the actual wires, but instead just swap out one of your speakers — preferably the one without the volume control — with theirs. Now they’ll still hear their own system sounds from the remaining speaker, and as an added bonus, they’ll have no way to control the volume of your annoying antics.

If your budget doesn’t have a tab for “pranking gadgets,” you can always go the manual route and utilize the USB port to attach a second mouse to a neighboring tower. This works especially well with a person across from you, if you can get under your desk and access the back of their computer. Plug in, wiggle away, and watch them squirm. Added points if you have a wireless mouse.

Taking the Annoy-a-Tron up a notch, the Phantom Keystroker actually plugs into a USB port and then makes random key presses or mouse movements every few minutes. You can control the frequency and the kind of emissions. For $25, this may be worth every penny — especially if you can write it off as a business expense.

A small investment will have a big payoff with the ThinkGeek Annoy-a-Tron. This little $10 gadget can brighten even the dreariest of offices. It looks like a computer part, but when you flip the switch, this fella sends out annoying beeps and buzzes at random intervals. You can toggle between different grating sounds, too. The thing is magnetic, so you just slap it on the back of someone’s computer and watch them try to figure out where that awful noise is coming from (hint: they never will).

While you’re in the Word or Outlook settings, another good place to tamper is the dictionary. Replace a few correct words with common misspellings just for giggles. Just be sure to let this one play out and get resolved before your co-worker sends any official memos to the entire corporation.

There are few things funnier than forcing a friend to insult himself — and Microsoft has made it easy to do just that. Take a moment to edit the Autocorrect feature in your colleague’s Word or Outlook (it’s in the Tools menu in both programs). Add a new entry to replace their name with “douche,” and watch how much more interesting all their emails and documents will suddenly become. A little creativity can take this one in plenty of different and equally entertaining directions.

A classic computer prank never goes out of style. The desktop image trick has been around for a bit, but rest assured: There are plenty of unsuspecting victims still to be found. Just head over to an unattended computer, minimize all the windows, and hit the Print Screen key. Paste the captured image into any graphic editing program — even Microsoft Paint will do — then save the file and set it as the desktop background. Then, all you have to do is hide the actual icons on the desktop — put them in a folder somewhere — and your victim will try endlessly to click the nonexistent icons, which are actually just part of the background image. For another variation, leave one program open when you capture the screen and watch as the person tries to click on it, type in it, and close it to no avail.

While we’re on the topic of system startups, the Windows Startup folder is a fantastic place for fun. Create a text file with an amusing message and throw it in there so your cubicle mate will get a daily greeting — or, if you really want to get evil, add in the restart shortcut from above (not recommended unless you just want to get your ass kicked).

We start with one sure to throw off even the most advanced Windows user. Setup is simple and you need only a few seconds alone on someone’s computer. When you get a chance, sneak over and right-click your pal’s icon to Internet Explorer or some other commonly used program. Edit the properties and change the target to: “%windir%\system32\shutdown.exe -r -t 00″ Now, every time your buddy tries to run IE, his machine will mysteriously restart — and your laughter will instantly result.

Pour some detergent down inside the garden hose. The next time your victim goes outside to water plants or grass. There will be a soapy mess everywhere.

Tie a rubberband around the pullout hose lever thats in your sink. Whoever uses the sink next will get hosed with water.

Leave someone's furniture in a 99% disassembled state.

Take a transciever like the ones ham radio operators use (3 watts or more is good) and push transmit while near a TV. Will have the effect of semi-scrambling whatever is showing. The more powerful the transceiver, the more the TV signal gets messed up. This does work on cable TV.

Rent porn tapes from the video store and record something like Barney or the Wizard of Oz over them. Just imagine the next person who gets them. Better yet, do it the other way around or exchange the tape in their respective cases. (they aren't likely to check)