I am considering moving my hardware to another case. I have a Compaq and a HP desktop. Are the instructions provided with new cases sufficient for an inexperienced person too safely relocate the motherboard to another case? I plan to make the change for either, or both, depending how the first works out. I have one Athlon 1800+ and one P3 650.
It may depend on which machine is which. Compaq formerly used custom motherboards, as did HP, but Compaq persisted later. Compare the two motherboards. One giveaway is power supply connectors, another is mounting-hole placement. Yet another is back-panel layout -- on an ATX motherboard (the current standard), most of the connectors fit a standard layout, and if they come close to matching, that's a clue.
As far as case assembly instructions go, it's not really hard. There are books available, as well as a variety of Internet sites that provide some basics; Google is your friend. If you can find the original equipment manufacturer (OEM) and their model numbers for the motherboards, all the better--you can download the user manuals, usually in PDF format.