I think I changed the permissions for the hard drive and now my MacBook Pro won't load. I can access the terminal using the OSX install disc.
What are the commands required to reset the permissions for the hard drive?
Start up from the install disc, run Disk Utility (it's under the Utilities menu), then select your regular startup volume (the volume, not the entire disk) in the sidebar, select the First Aid tab, and run Repair Disk Permissions.
That should fix things to the point where you can boot normally, but it may not be quite right because the version of Disk Utility on the install DVD is probably not the version you're actually running. So, after you restart of the hard disk, rerun the repair procedure on the live system, using the Disk Utility on the volume you're fixing.