This is always my favorite prank for this time of year because of the horror it tends to elicit in its Linux-using victims. A few years ago there was a version that made Ubuntu 9.04's GNOME, but today there's an for Ubuntu 10.04 that produces the appearance of Windows 7. Imagine their surprise when they find themselves suddenly catapulted into a Windows world! The fun just doesn't get any better.

2. 'Swap' Office Software

In a similar vein, fans of free and open source software tend not to use Microsoft Office for their needs, so that's another great way to mess with their minds a little. A fun trick is to on OpenOffice.org, for instance, with a that makes it look like Microsoft's product is launching instead. Bwahahaha! They'll never know what hit them.

3. Tamper with Autocorrect

No matter which office software they're using--hopefully by now it's --you can always get a laugh by tampering with the word processor's autocorrect feature. Why not replace all instances of "windows" with "Linux," for example?