PLEASE HELP - powerbook G4 boots to blank blue screen

[incogneato]

First, I'd like to sincerely thank you for your time and help.

I recall accidentally moving my library folder into another folder, so I tried pulling it back to the original folder. However, a prompt appears & tells me that there is already a new version of "Library" & if I'd like to replace it. I didn't know what to do- the new Library folder had another folder inside that says: "preference". I didn't know whether to copy that folder over into the original Library folder and then deleting that new Library folder and then pull that original back to the original folder. I ended up replacing that new library folder w/ the original one when I pulled it back over to the original folder in "Users". Everything seem find after that. I decided to download a program for cleaning up my mac at the mac site, then all of a sudden while mounting, everything closed. (not sure if mounting was complete or not, I didn't install anything.) The only things that were left open was what I was using: quicktime, safari & firefox. When I quit those 2 programs, I was surprised to see that my finder wasn't there. I tried to access it from the dock menu but it said that finder wasn't running. I tried restarting but I keep getting the grey screen w/ the dark grey apple and then it finally goes to the blue start up screen with the shiny apple and MAC OS X, following that a blank light blue screen appears w/ nothing on there except for a useless cursor. Please help me, I'm pretty good w/ pc's but know nothing about mac. I appreciate your help!

p.s. I remember updating the quicktime software last night too