Mac mini won't boot up.

I think I did something a bit stupid . I right clicked on the hard drive icon and then on GET INFO and then changed the priveleges to READ AND WRITE for it and EVERY file within it....was that bad? Only now the computer won't start up at all, not in safe mode and not from an OS X installer disk (not a mac mini one though, it's from a macbook).

Any ideas? I also deleted a .plist file but that wouldn't cause this to happen would it?

The MB system restore disc will not work as they are model specific only. Yes it was bad and you may well have to go out and purchase a Leopard retail install DVD, try and boot from that and repair disk etc., but you may have to format the drive and do a clean install