macpro powerbook won't let me log in

[anilmistry]

hi-
I have a dual core mac powerbook (osx 10.3.9 i think) - it has suddenly decided to stop accepting my username and password at login (shakes it's head)- for a while, previously to this it was sometimes taking a long time to start up after i logged in, and now it won't allow me in at all.
I've tried to install osx again (restart with disc in whilst holding down c) but when i do this, an image of the hard drive comes up instead of an image of the disc.
I've also tried alt-apple-p & r upon power up, but no response. I've copied my files off it by linking up to another mac via firewire as a safety.

PLEASE HELP!