Thank you all SO much for your help
My HD is extended, so that's good, and the CD drive ID is 0 which is good too.
The disk I have is a copy from a reputable source... It's generic so should work on most Macs.
I'm now going to read all the Mac OS X stuff from the links and try again, wish me luck and thanks once again, I'll keep you posted.
My computer is not going to get the better of me!