PowerBook - Boot Drive Was Filling Up, Restarted, Now only boots in Darwin?

I have a G4 Powerbook running Panther. My drive was just about completely full and everything was starting to run very sluggishly, I was also getting those hard drive capacity warnings. While I was figuring out how I would clear up space everything started freezing up, it told me I needed to force quit some apps to clear up memory and I did. I then restarted my computer figuring I would restart, then deal with freeing up space. I restarted but now when I get to the login screen it immediately goes to the black Darwin command prompt window. I am not very familiar with Darwin and I'm not sure what to do. Is it doing this because my hard drive is full? Is there a way I can transfer all my files to an external drive via: Darwin? Is there a much simpler solution?

Thankyou,
Sam