Panzer Campaigns Stab Version 1.4 Update 5

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BTW, my games aren't in the registry because I didn't install them the old-fashioned way; just copied them from the backup of my old computer.

That is why Stab cannot find them. At a minimum, run Regedit and add for example the following key:

HKEY_LOCAL_MACHINE\SOFTWARE\HPS Simulations\Moscow '41

It does not need values under this, it must just exist for each game you have. Then Stab will go looking for it.