At my office we all use Macs. Our favorite past-time in meetings where people are projecting is to use our Apple remote to hijack the computer of the person presenting. This is especially funny if the presenter is in the marketing department as they'll come up with all sorts of funny explanations as to why their computer is wigging out.

If you want to keep someone from hijacking your Mac with their remote, you have two options. For both of them, you need to go to System Preferences, and then choose the Security icon.

Once there go to the General tab. You can check the box next to "Disable remote control infrared receiver" and your computer will ignore all remotes. But if you want to use your remote and just block others, don't check this box. Instead you'll want to click on the "Pair..." button. You then hold the "Menu" and "Next" buttons on your Apple remote at the same time until a graphic pops up on your computer letting you know that your computer has been paired to the remote.

This will protect you from happy tricksters in your office who attempt to hijack your Mac.

By the way, you can have a lot of fun with your remote at the local coffee house this way. Just find a really high-end, arty, coffee house with a lot of Macs in it. Hours of entertainment will be yours.