On Windows 7, when I first clicked on the "Populous the Beginning" link on the desktop, it asked for a resolution. I tried 1280x800, but realized it didn't work out well and I needed a higher setting. So I closed the game and wanted to select a new resolution. I've been trying to figure out how to get this Resolution Selector window to show itself again, but it never shows up anymore. I went to the game directory, and tried GOGSetup.exe and GOGLauncher.exe but neither one would allow me to change the resolution anymore, they just launch the game. Is there a way to fix this?

To get the setup to pop again, you have to go into your Populous 3 folder in the start menu and select the setup from there. If that's not there then it may be worth uninstalling and installing again. Unless it's hidden in your install directory?

I tried all the .exe files in the Populous 3 directory, but none of them would bring back the Resolution Selector window. It looks like a bug. Is there any other way to fix this without having to reinstall the entire game?

Go to your Start menu; All Programs; Gog.com; Populous - The Beginning; Setup..

OR:
If you've deleted the start menu folder or it isn't there for whatever reason, you can do it another way: Open up your command prompt (run CMD.exe); browse to your install directory (by default you can do this with "cd C:\PROGRA~2\GOG.com\POPULO~1\"), and then run the command "GOGSetup.exe SETUP".
Hope this helps.

I navigated to the Populous 3 directory in the DOS prompt, and tried the GOGSetup.exe SETUP command like you said, but it did not work. When I try to run just GOGSetup.exe it just runs the game, but refuses to allow me to re-set and fix the resolution. Is there a way to report this bug to the GOG.com developers?

From what I've heard, the fact that the program itself simply boots the game from the second time onwards is a "feature not a bug", so that you don't have to go through the splash screen every time you start the game. That said, with the SETUP switch it *should* work - that's exactly what the setup shortcut in the Start menu does, and it works perfectly for me from command prompt too... When you say it doesn't work, what do you mean? It just boots the game, or it comes up with an error of some kind? There shouldn't be any reason for that not to work, just literally GOGSetup.exe SETUP and then enter ought to do it.

Deeper into the rabbit hole we go... have managed to find the way of fixing it once and for all, but it requires trawling into your registry. (please be careful here)

Run regedit (from your run box), and then go to HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\GOG.com\GOGPOPULOUS3. There will be a string there titled "FIRSTRUN", which tells the setup program whether it needs to bring up the setup page when you run it. The value will currently be set to NO. Double-click that and change the value to YES. Then run GOGSetup directly from the installer folder, and it'll bring up the settings page.

(note I'm on 64-bit, if you're on 32 it might not have the Wow6432Node folder in the path, in which case it'll most likely be HKLM\Software\GOG.com\GOGPOPULOUS3)

Hope something out of all this works for you! =)

If you need to contact GOG at all, click the support link at the top of the page. If the setup shortcut in start menu isn't working then it could be useful for them to find out.