Dismantling and bent pin. There's two logic inputs that come together.
That's just the kind of thinking that us old-timers used to use on valve electronics.
There is no need to have the monitor plugged in for the early tests.
Is there a disabled VGA graphics system on the MB? This might be reinstated to do the diagnostics - once you've eliminated the monitor.
Taking time and thinking. Just look at the MB for a while. Tiny screws etc. shaken under the edge. Anything that could have fallen onto cards or memory during the moving.
Are we to understand there are NO 'Post' beeps? Definitely remove the USB units, as I said, they are easy and carry a hard 5v. Certainly enough current to fell the PSU. Hard drive? I should have mentioned that when I talked of pulling the CD power lines. Same sort of procedure.
As far as I know, there are no 'special' USB plugs for required items like keyboard. Anyone know different?
I would be doubtful about the BIOS at this stage. Having said that, I owned a laptop that was a Sony write-off at two months old, that was just a BIOS chip problem. But very unusual. By the same token, the memory will come well down the list because it would not have been affected by the temporary packing away.
The dismantling, preceding the fault, is top of the list to focus on I would have thought. Go right round the 'rebuild' again, leaving out what you can.