Away From Home
Change the victim's homepage to something unexpected. Open their browser and choose Tools->Options and enter the URL for a new page.
On a Windows computer (I know this works with XP, but i don't know about earlier or later systems), open the task manager by pressing Ctrl+Alt+Delete. Click on the processes tab and find "explorer.exe." Click on it and then select "End task." This will cause all the shortcuts, the taskbar, and the start menu to disappear. (The cure: open the task manager again and choose "new task" from the File menu, then type "explorer.exe".)
Submitted by JoeDawg
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. Be sure to write "April Fools!" on the note! (Note if they have a standard mouse, you can perform the same trick by taping a piece of paper over the ball underneath the mouse.)
Click on Start > Control Panel > Mouse > Pointer Options and check the box next to Display Pointer Trails. Next time someone uses the mouse, they'll get a surprise.
Sneak onto your victim's computer and change their default font color to white. This will cause momentary confusion as their writing will suddenly be invisible.
Reminders From the Future
If you can access the victim's computer anytime before April Fool's Day, go into their Outlook calendar and set up some random appointments for far into the future (several years into the future so they won't notice them). Then set them to give automatic reminders on April 1st. Make them as goofy as possible!
Go to Start > Settings > Control Panel > Mouse > Pointer Options, and change the mouse pointer to the slowest speed. If your victim isn't very computer-savvy, and doesn't know about this setting, they won't understand why their cursor is suddenly moving slower than a snail!
Can't Close It
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. Then save the images as a file. Next, right click on the desktop, select "properties", and browse for the image you just created. Select that image as your background (make sure that it is stretched and not centered or tiled). Your victim will think he has the application open on his computer and won't understand why he can not close it or minimize it.
Submitted by Rich