Recently I upgraded my laptop from Snow Leopard to Lion. However in Snow Leopard, I fooled around with the system a bit and "named" an app called LaunchPad.app(It's actually called quickpick) Now in Lion, it retained the old app and didn't change it to the actual LaunchPad. When I try to delete the LaunchPad app now, it says the it is necessary for the system and I can't delete it. What should I do now? Thanks everyone.
Create a Time Machine backup of your current system, reinstall Lion, restore everything but applications from backup, then restore the other applications manually from Time Machine.
If you're feeling adventurous, and have good current backups, you could launch Terminal and enter the following exactly as shown:
sudo rm -rf /Applications/LaunchPad.app
Enter your password and the application should be removed.
Now you shouldn't have LaunchPad.app anymore. You could try to get LaunchPad from a friend, by installing a 10.7.2 combo updater, or by reinstalling Lion.