Land Rover Repair: Disco II wont start, ground cables, passenger dash

Question
I have a 2002 Discovery II. After driving it this weekend, and getting home I went to park it and shut off the ignition but when I did the engine kept running (I think as the sound did not exactly resemble an engine running) so I turned the ignition back on then off. Now when I turn the key to start it nothing happened, except a faint click from inside the fuse compartment and it sounds like one under the passenger dash. The radio and clock dims when key is turned, then return to normal after I release the key. In an attempt to correct the problem, I have changed the battery, and starter but no change. Any help with direction to follow would be immensely appreciated.

Answer
It's hard to be sure from your description but it sounds like you have an electrical system failure. Since the truck stayed on when the key went off I'd check the wiring through the switch.  Next I'd check the power at the starter, then the fusebox, and follow it to the big connections at the alternator and battery.  Don't forget the ground cables - they are the other side of the circuit.  I think you will find your trouble in there.   You'd be well advised to buy an electrical troubleshooting manual and workshop manual for this task