The PC is running Fedora C5 and KDE 3.4. WHenever I shutdown the computer, the screen turns to black with a mouse pointer , nothing I can do except wait and wait. Finally I turned it off by the power button.

What's wrong ?

What can I do ?

How are you shutting it down?

Logout->turnoff computer

What happens if you use the commands 'halt' or 'init 0'?

I've seen failing shutdowns on Fedora when some processes are hung on IO.
When you are at the black screen, try pressing Ctrl-Alt-F1 (or F2, ...).
It should bring up a command prompt, from which you can for instance check for hung processes (using the "ps" command).
If that works, you can use Ctrl-Alt-F7 to go back.

It's also possible that some of your "kill" scripts in /etc/rc.d (or etc/init.d) don't work like they should.
Basically, when you shutdown, those scripts are called, in a specific order (see "man chkconfig"), to shutdown
all services and stuff. If one of those hangs, your shutdown may be interrupted too.