Installing a new game deactivates the previous Registry edit, so use the Registry edit twice: before installing the game and after installing the game.
I checked it in the process of installing and running licensed versions of the old games “No One Lives Forever 2” and “Contract J.A.C.K”.

I designed the Registry edit files as an Archive, this Archive also contains a list of 2072 old games that are controlled by the “Game Explorer” for Windows 7
Download Archive here, read help, [delete Spaces in this link]:
BLOCK_GameExplorer.zip (40Kb)
h t t p : //www.mediafire.com/file/24e176643j9cj2r/BLOCK_GameExplorer.zip/file

Why hasnt GoG fixed this yet?
I have all my games and a copy of Windows 7 backed up, this is a huge problem.

GoG has no right to fix it.
"Game Explorer" is a Windows 7 system program; it is owned by MicroSoft.
Windows 7 is not serviced right now, so MicroSoft will not upgrade.
MicroSoft invites you to buy and use Windows 10

:) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :)

Good idea! Tweaking software often causes your PC to BLOW UP! I advise you to contact a bomb disposal team to make your games work without problems.

I'm not saying that the offered solutions don't work, I'm just saying that I don't feel competent enough to try them out. I might screw up and delete system32 or something without realizing it

I think it's paranoia
I have not used any Antivirus for 5 years on my Windows 7x64 SP1 Professional system.
Instead, I saved my system 5 years ago with Acronis.
Now, if my system starts to work unstable, I just restore my Windows 7x64 SP1 Professional from the old copy - this process takes only 5 minutes, and I again have a clean system.
I never had any problems.
Of course, I do not visit hacker sites. :)

Here you go: I created the .reg files for you so all you have to do is run them.

Download the .zip file from here:
https://www.dropbox.com/s/jd0tiobpzk0wayd/gameuxfix.zip?dl=0

Extract both .reg files.
gameuxfix applies the fix
gameuxundo undoes the changes in case anything goes wrong

Oh so this is why my games suddenly stopped working. I was playing Gothic 2 like 3 weeks ago and had a crash, next day i couldnt launch the game at all, fast forward steam summer sale i got hl2 and surprise surprise it doesnt work so i was like damn gothic 2 broke my pc like wtf. Thank you for your register fix, games now run again.

For those who dont want to mess with registers i found this solution (worked on 3 games i tried):
1. Launch your old ass game
2. Wait for rundll32 to start wrecking havoc
3. Launch your game again, it should start now ( dont kill any process)
4. Simply alt tab and end rundll32 process
5. Play

It's pretty easy and safe if you use this kind of guide:

https://www.wikihow.com/Use-Regedit

Ensure you make a backup first if your really worried or at the least copy down exactly what you have changed to be sure you can undo any changes.

In general the advice given in the first post is very easy to use alongside the guide above and you should be able to do it yourself. Better that than trusting downloads from random people on the internet imho.

Thanks for the advice, I might follow it if the problem shows up again. Thankfully it's gone for now though.

The other poster may very well just be a nice guy, but I'll never download something from a stranger.

There is an easy way to disable the “Game Explorer”, which blocks the launch of your game on Windows 7.
This method is based on the fact that “Game Explorer” identifies the game by the name of the launching file.
Open the game folder and rename the launch file, then “Game Explorer” will not block your game.

For example,
- for the game "Far Cry", rename FarCry.exe to FarCry_1.exe
- for the game "Half-Life 2", rename Half-Life 2.exe to Half-Life 2_1.exe
- for the game "No One Lives Forever 2", rename NOLF2.exe to NOLF2_1.exe
Etc., Etc., ...
Then create a new shortcut for the renamed file and copy this shortcut to the desktop.
Use the new shortcut to launch the game.
Now your game will start instantly.

P. S.
This is the best way for paranoids. :)

Yeah but program compatibility settings is also dependent on the exe's name, so renaming it will break any compatibility setting, which might be a problem for some games, forcing you to re-do it manually.

You can use this method "renaming the launching file" only after full installing and upgrading the game.
After renaming the launching file, you need to do the same manipulations that you did with the old launching file:
- Install compatibility with Windows XP (if necessary)
- In the "properties" of the new shortcut copy the parameters of the old shortcut (if necessary)
- Change your Firewall settings (if necessary)
... For most old games, these options are not used (except for compatibility with Windows XP)

The advantages of this method are:
You do not change the Registry, you do not change the system files and do not use any programs.

I changed the server address contained in the "Games" chain value to 127.0.0.1 and it works by now. Old games starting at the first run and no rundll32 melting the CPU at all.

Thank you guys!