installed 10.4, but can't login


I just installed 10.4 from a family pack onto my 17" 1.5Ghz G4PB.
and after the restart, my account name or password no longer work.

I have connected the PB to my G5 in target disk more and everything is there
my account , folders docs, the lot. But when I boot the PB I can't login
I just get the vibrating login dialog when I click on login.

I know my password and ID, I type them 20 times a day after my screen saver cuts in .

what can I do ?

Thanks for any advice
Let me know what happens ALMOOK cuz I just bought Mac OSX 10.4.3 Family-Pack. Been having some issues with my root login PW currently on 10.3.9.

(about to install Tiger but don't wanna screw up the whole thing ya know!)