Correctly Shutting down system thats hanging
 

I've been told you can shut down a system thats froze (while in X) by hitting ctrl+alt+delete and/or ctrl+alt+backspace etc...nothing has worked for me. I cant find any documentation on this...can anyone help?

If you have a total lockup and nothing responds, then you usually have no choice but to do a cold shutdown or reset. But if its just a program or X, usually the ctrl-alt-delete or ctrl-alt-backspace will do the job.