pyro

I need help..I was playing with OSX themes and the GUI, changing dock visibilty and crap and it wouldnt detect my internet connection..(i have cable) so I made a new user and tried loggin in that way, and now it wont even boot up.. it stays at the blue screen before the icons and desktop icons would come up..help! How can i restart it???

I have a powerbook g4 800mhz on OSX