A full system crash is very rare in Linux, most of the times it is only one program that acts up. There are several ways to recover from a crashed program.
1). If a program blocks, crashes or runs-away ( does not want to close or stop running ), change desktop and press the Ctrl+Esc keys. You will get the Process Table with all processes running on your system ( some
processes may appear several times, that is normal ) the first four columns are the most important, if you know the name of the process things are simple, if you don't: in the 3rd and 4th you can see what is consuming
all that cpu. Now remember or note down the PID number ( Process IDentifier ) you will need this. ( for multiple processes with the same name only the last one is the one you're after ).
Now go to yet another desktop open a terminal/console type < su > ( without the <> ) and give your root password, then type < kill 4246 >; ( if 4246 was the pid number ).
That's all, job done ! ( rebooting like in Windows is NOT needed in Linux !)
(There are other ways with names instead of numbers, terminal instead of gui process table, but this is the most general way to solve ur problem )
2). If all your desktops are blocked ( when X crashes): Press Ctrl+Alt+F1, you will go out of X, and get an empty terminal screen, fully black with a login prompt. ( there are 6 terminals available F1 to F6 ) Then log in as
"root" ( not "su" this time ) and type <top>, you will get the same process-table with the PID numbers, find the number that's hurting, close top with the"Q" key, press Alt+F2, you will get a second black screen ( terminal )
to log in to, log in as root and < kill 4246 >.
For returning to X, press Alt+F7 !
3). Also you can try Ctrl+Alt+Backspace . . . it will log you out of X and bring you back to the graphical login screen where you can start KDE or Gnome again.
4). If even this does not help or you can not find the process and PID number just type "reboot" at the root-prompt ( of a Ctrl+Alt+F1 terminal ) and you will get a clean reboot.
5). If even this last step does not work, read the POST: Skinny Elephants
