The Dell 2400 is quite old by today's standards... and hard drives are failing frequently now. I would suspect the hard drive couldn't tolerate the vibration, jiggling, and impact of the move.
However, since it is a problem connected to a move, I would remove the case cover to unplug and reseat each cable... hard drive, optical drive, power supply, motherboard. Use a little compressed gas such as dust-off to clean out the cpu fan, then (while using rubber gloves or plastic bags) remove and reseat all the memory modules to assure they are plugged in firmly.
In anything you do, use a lot of patience. Older components become brittle and crack easily, requiring replacement.
Then get back to us for more useless advice.