How do I change permissions from Custom back to Read & Write? (when I try it pops back to Custom)

I have a problem where when I click on my internal HD I get a message that I do not have sufficient access to open the folder (actually a drive). When I do a get Info on the drive it shows Custom for all the permissions and will not allow me to change back to read and Write. When I use Disk Utility the Verify & Repair Permissions buttons are grayed out (Whether I have booted up from another internal HD or the install disk). I am baffled since I need to access the files on the drive that the Mac pro has locked me out of. Any help greatly appreciated.