My entire identity,mail, files, password all disappeared

[sweeybaby9]

I have a powerbook G4 running Leopard, Mac Mail. My power was lost and when I rebooted my entire identity was gone. I had to create a new user name as it would not take my old one. I have lost everything. In the weeks prior to this my mail and address book were freezing up, I ended up having to remove the address book application altogether as well as Entourage and then rebuild my mailboxes. Afterwards when I would receive emails and I opened them from people who were in my personnel address book prior, the system would still freeze, now everything is completely gone. My other desktop computer is running Tiger and everything there is fine. How can I get my files, pictures folders etc. back?