It won't turn off because the power down driver hasn't been loaded, I would
point to a mother board fault. A loose connection somewhere would point to
this fault as well, try pushing every connection into place. If this doesn't
work try resetting the BIOS, to do this check your motherboard manual. It
will involve moving a jumper round on some pins, turning on the computer
resetting the jumper then restarting it.

Dell XPS 800, was working perfectly before a move.

Need your help with diagnosis, here are the symptoms, when turning it
on:

green power light comes on, hard disk normal sounds for about 1-2
seconds.

No beeps, blank screen (not even a cursor).

Box will then not turn off at front power switch UNLESS I hold it for
7-8 seconds, then powers off.

Looked inside and found no obvious signs of damage or loose boards.

Any ideas? (Don't suggest dell support they did not reply to my inquiry).