[Jester]

If you use the restore discs they will wipe the computer. If you want to make sure they wipe the computer when you put in the disk and it brings up the operating system from the disk you can go into the disk utility (it is somewhere in the menu bar) From the disk utility select the hard drive and go to the erase tab. Volume format will be Mac OS Extended (Journaled) and the volume name can stay untitled or you can name it.

As for erasing. You can hit ctrl+mouse click and it will bring up a menu and an option will say move to trash. Or you can do it all at once and hit the apple key+delete (the backspace key on the mac keyboard is the delete key). Hope that helps.