What web browser are you using as you can usually launch files from it.

Firefox click the big blue down arrow that appears next to the address bar and click on the exe.

Chrome/(new Edge) click on the exe at the bottom of the screen on the bar that appears when you start downloading anything.

Your problem seems unique somehow, so I suggest you contact support.

If you have downloaded all of the offline backup installer and executed it and followed the install process through to completion (with no error messages), then it will be installed on your computer.

Based on the nature of your post, I suspect that it will have installed to the default location. I can't remember where that is as the installers remember the last location you installed to; it might be under Programme Files.

Use file explorer to search obvious install locations. You could look under "Programmes and Features" in the Control Panel to see whether windows thinks it has been installed.

The above assumes that you're running a windows based system and a basic knowledge of the operating system.

Other than that, it's not that easy to diagnose the issue without more detail.

Did you actually install it, or did you think downloading it meant installing it because that's how clients work? If you downloaded the backup installer it will be in your Windows download folder as an .exe file, then you double-click that to install the game. The install process will create a shortcut on your desktop to launch the game.

Also worth noting GOG's offline installers have multiple parts for games this size, so if you only downloaded one of them or some of them it won't install.

Ooh - so you haven't actually installed anything - you've just downloaded a file that you then need to execute. Look in your downloads folder.

To be absolutely clear: you have double clicked the exe file, you've seen a window like the one I've attached, you follwed through with the installation, and the game is not in the location that was displayed in that window?

Well, at the very least this mean you never pirated a software from the webz. Good for you XD

I didn't use a browser, I used GOG galaxy. It's not in the downloads folder, I checked quite a few times.

I guess have a brain tumor and I hallucinated installing the game. I'll just install it again.

Offline Backup Installers are ment for a browser not Galaxy. If you are installing the game through Galaxy then go through Galaxy.

In Galaxy click on 'Owned Games' or 'GOG Games' this will list all games you own then find the game you want to install.

Edit:

Then either right click on it and click 'Install'. Or left click and click on 'Install' at the top.

So... all this was somehow about Galaxy and not the offline installers?

I am assuming here you are using a Windows PC. If you are a Mac user, I can't help because I know nothing about Macs, nor want to learn anything about them.

First of all, did you download the offline backup installers with the GOG Galaxy client, or a web browser? EDIT: Ok you said later you used Galaxy, fine.

As I don't use the GOG Galaxy client myself, I do not know where GOG Galaxy downloads the offline installers (if you chose to download them with Galaxy; I guess the download folder is mentioned somewhere in the GOG Galaxy client options), but most if not all web browsers (Edge, Chrome, Firefox) download files by default into your Windows Downloads folder.

So, open File Explorer and head to your Downloads directory, maybe you see your downloaded GOG installer files there.

If you are still wondering why there are two ways to download and install GOG games (the "offline backup installers" and clicking on that magic Install button on the GOG Galaxy client), the "offline backup installers" are the original way how GOG games were provided by this store. You downloaded the installer files with your web browser or a separate downloader application, and then installed the game just like you'd install any normal Windows program that is provided in an installer format.

The GOG Galaxy client came later for people who find that old way too "archaic" or "cumbersome" and want Steam-like features like automatic updates, cloud saves and social features. Still, many of us prefer using the original offline installers because they are easily archivable, and are fully usable even in the future if and when the GOG store closes its doors for good. When you have those installers on your hard drive, installing and playing those games doesn't depend anymore on the existence of the GOG store/service.

How so? Galaxy downloads the offline installers the same as a browser and the old downloader did.

You can download the offline installers also with Galaxy. Seriously, you didn't know that, even though it has been repeated in these discussions a couple million times before?

YES, OFFLINE BACKUP INSTALLER CAN BE DOWNLOADED ALSO WITH THE GOG GALAXY CLIENT.

ALSO REMEMBER, WHEN NEW USERS ARE ASKING FOR INSTRUCTIONS, QUITE MANY, IF NOT MOST, OF THEM ARE USING THE GOG GALAXY CLIENT ALREADY, SO ALL YOUR PRECIOUS INSTRUCTIONS WITH PICTURES OF HOW THINGS WORK WITH WEB BROWSERS GO IN VAIN. THEY DON'T HAVE THE SAME VIEWS AND BUTTONS ON THEIR GALAXY CLIENT AS YOU HAVE IN A WEB BROWSER. SO IT IS ALWAYS BETTER TO FIRST ASK WHETHER THE USER IS CURRENTLY USING THE GOG GALAXY CLIENT, OR THE WEB BROWSER.

Phew.

Yes, thank you, I know that. But everything the OP wrote before implied using the offline installers only, and frankly the way he writes nothing of what he's actually doing was very clear to me. I guess he didn't use enough capslock.

I didn't know that - you learn something new every day.

To be fair, it's not right to blame the people trying to help (which you might not be, but the CAPSLOCK text certainly gives it an air of blame). Users requesting technical support should give sufficient details over what they're doing to enable the community to help. Reading OP back, until post 23, it read like someone using a web browser to download the files.

Community got there in the end though, so that's a win.