try this...su to root, 1nc in root type password, it should prompt you for a password, then type the password you want to use hit enter, it should ask you for a confirmation then retype and that should reset your password.

just curious, how did you do the hd install? it sounds like you are still booting from cd which would implicate that you just copied the boot iso to hard drive rather than a full hd install. If that is the case look this over:

http://www.distrowatch.com/dwres.php...review-knoppix