Customization problem

[Kragtast]

I was messing around with shapeshifter and custom icons, as well as dragging out folders like Documents, Applications, Pictures, Movies, Music onto the desktop. After this, all the Applications folders on all accounts only contain a non-functioning version of iTunes, save for the folder I dragged onto my Desktop.

Can I reset my computer defaults?

What do I do?

 

[Rhisiart]

Back up important files and then using your original MacOS installation discs to do a 'Archive & Re-install' of the operating system.