Computer wont shut off

[PCFetish]

I changed PSU and the case
those were old stuffs
fresh installed XP and now when Shut down it just shows black screen with "now it's safe to turn off"
power button on the case doesn't shut off
is this old PSU and case fault?

 

[DaTT]

Hold the button down for 5 seconds or so

 

[CarpeDiem99]

Hold the power button until it shuts off, then power it up and shutdown and see if this happens again.
CarpeDiem