Yes I agree. Unfortunately you apparently installed the Galaxy client (while installing the game) unknowingly, and you have some trouble running the Galaxy client, for which reason you can't run the game either. Not really your fault as GOG has chosen to "trick" people to install the Galaxy client, by enabling its installation by default, and hiding the checkbox behind the installer options.

Many people (me included) opposed GOG's decision a couple of months ago to embed the Galaxy installer to the game installers, as I feared it just makes it harder for new users to comprehend as they unknowingly install the client, and it is yet another option for ways you can install your GOG games.

It is unclear to me whether you now have the Galaxy client installed, or not. You have said you have at least tried to uninstall it, so if you still see it running, apparently that uninstallation failed.

You mean it tries to start the Galaxy client? Then it seems you still have at least some remnants of the Galaxy client in your system, as the shortcut tries to run it if it thinks Galaxy is installed.

What was the error the first time "it wouldn't install"? Hopefully you haven't now installed the game twice, to two different places?

I don't have the game installed at the moment and I don't recall for sure which exe it was and in what directory, but take a closer look, also under subfolders. I have a recollection it would be "TW3.exe", located under the "bin\" subfolder, but I could recall wrong as well. And I am of course referring to the folder where the actual game is installed, not e.g. the Start menu shortcuts or anything.

When you locate that exe file, try to run it directly, possibly as an administrator. Just to see if your The Witcher 3 runs fine without the Galaxy client, which then suggests you just have problems with your Galaxy installation. You can still play the game without the client.

At this point it doesn't matter. Reinstalling the game and unchecking the "install Galaxy" option will not help, you still have the existing remnants of the Galaxy in your system. All that unchecking does is not to try to install the Galaxy client (again).

Yep, it tries to run the Galaxy client (if installed) before running the game. Which is exactly why I suggested you try to find the Witcher 3 exe file and run it directly, as then you are not launching the Galaxy client but just the game. Just to see that your game installation works.

Yes, it doesn't have the option to install the Galaxy client, as the GOG Downloader downloads the so-called "classic" installers which don't have the embedded Galaxy client installer. The earlier installer you used at first probably had it.

As far as your (broken?) Galaxy client installation goes, I think you have two choices:

1. Try to fix the Galaxy installation, hopefully making the Galaxy client work on your system.

2. Try to get rid of the Galaxy installation, and run your GOG games without it (if you don't care for achievements, cloud saves and multiplayer support).

I'd personally go for option two, so these are the steps I'd try in order to get rid of Galaxy:

- Download the Galaxy client installer from https://www.gog.com/galaxy/

- Install it again to the exact same place you installed it before (I presume the default location), just so that it overwrites the earlier Galaxy client installation completely.

- Don't try to run the Galaxy client.

- Now uninstall the Galaxy client.

That is the way I have earlier been able to uninstall some Windows applications whose uninstall script had ceased to function for some reason.

For the Witcher 3 it is an a bin\x64 folder.