At drive C: i install only programs. Data associated is placed in other drives like D: E:
I installed Steam on drive H: and related games also on drive H:
All Ok
Recently, when i installed GOG on drive H: and one game also on drive H:, Windows system now identify my drive H: as a system disk
So, if i create one image of installed system, windows now wants to save drive C: and drive H:
Steam dont create this problem
I believe GOG install some part of its program on drive C: and how installation is on drive H:, Windows now see both C: and H: as system disks
Problem disappear when i removed GOG program AND installed games

Just so you know, you have the option to not install Galaxy to play games. Log in to your account on your browser (Use Firefox or Chrome), then access your game library from your username, and download from there. The installers should be standalone installations as well.

What you're describing makes no sense. Even if galaxy did install files on a drive you didn't want it to there would be no reason for disk manager to flag those disks or partitions as system disks or partitions. For a disk or partition to be flagged as a system one it needs to contain the boot loader for an OS... something galaxy is not installing.

Indeed... Although which one is 'boot' is the one it actually tries to boot from first. But a lot of this has changed since i got familiar with the Fat12/Fat16 filesystems.

Curiously the 'system' i have on my system isn't even one i have access to.

The system reserved partition is created when windows installs to reserve a portion of disk space for potential future use by the operating system. It’s a place holder for the os to have access to another partition if required.

Mhmm... I figured it is needed if it requires a boot partition, like if you compress the entire disk and there isn't enough code to decompress the NTFS portions it needs, the special partition could have a uncompressed bootloader. Also since Microsoft started locking files that are open, if doing a major update that replaces/changes files locking files on the special partition vs the actual system makes sense too.

Reality is the sense. I make image system backup regular and when i install GOG and games in other drives they are flagged as system, i say system for create a system image for backup. Try and you see, very easy Try, and you see drive is marked as system WHEN you try make a system image for backup

So you’re not talking about a disk flag in disk manager? The flag is being assigned in a disk imaging software? What flags are assigned to the disk in disk manager or if you run diskpart? What imaging software are you using?

I would trust the disk flags from windows disk management before a third party imaging software.

What software are you using to image a partition? When you take a pure dump of a partition it copies the data of that partition/HDD. Such imaging software will only read the bits and byte of the partition/HDD, it doesn't care about the software/registry installed. Like CloneZilla or Norton Ghost.

When you install a game is it through Galaxy or the off-line? When installing, does the installer suggest something like C:\Games\GOG\gamename or H:\Games\GOG\gamename?

When I install GOG games it checks the registry if something exists:

1. If it doesn't find anything it suggests the standard path, f.ex C:\GOG Games\gamename

2. If it does find something previously installed in the registry it, it shows that path to me like: S:\Games\GOG\gamename.

Windows "remembers" every paths software makes, usually in the registry. Even paths when you f.ex saves a text-file.

Galaxy also "remembers" the paths where you installed the games. As far as can be understood - there is nothing in GOG's games or Galaxy that would alter these kinds of system/disk wide changes (unless you dl from an unofficial source and it installed some nasty stuff.). They don't touch the disk manager, disk configs or bios for that matter, only the registry, which again, Galaxy and games reads from when installing, and then writes to it.

But, I could have read your post entirely wrong :-)

I use Windows program
Go to Control Panel -> System and Security -> Backup and restore -> Create system image
Windows search available drives to save system image and also check drives markes as system
Sure, i plug one notebook disk drive on usb door to receive system image
If my Windows give problems, i can reinstall all my windows
Or, i bought program WintoHDD and this program create on another drive one full clone of system drive C: or other drives.
In this case, i just remove disk with problem and insert drive with Windows clone and run ok.
I did that when i changed my 1TB disk for a new 2TB disk

Alright, well windows backup should be pulling directly from disk manager for disk flags, but it's hard to help you with that unless you can show us what's going on. I would have to see a screen shot of the behaviour in windows backup before and after install and disk manager before and after install to get a better idea of what the problem may be.

I have Galaxy installed to my E drive, and it is not marked as a system drive... So... I can't speak to this as experience.

Go to Control Panel -> System and Security -> Backup and restore -> Create system image
Windows search available drives to save system image and also check drives markes as system
Sure, i plug one notebook disk drive on usb door to receive system image
If my Windows give problems, i can reinstall all my windows
As i said is marked as system WHEN you create a system image as above

Why i bring this ?
I dont want make a system image backup at a disk drive installed in a usb door, and also save a game drive.
This use much more time and space and game backup is not relevant.