Following a recent failed attempt to run the GOG Galaxy 2 client on my Windows 11 PC. I uninstalled it and attempted to re-install it. I got the following error message around 75% into the installation. I have run CC cleaner to remove any remaining files from the original installed client but this folder remains in place and I can't doing anything to update or remove it manually.

If you need to uninstall anything on your PC use Revo uninstaller it uninstall everything (reg too), there is a portable version.

You have an access denied
Try to be adminstrator to install GOG
Or change the owner of the folder (propriety>security)
Try safemode to erase the folder
Otherwise try google

the reason is Windows 11 lies to you about having adminstrator rights when it locks your system files... this is by design because Microsoft knows best

there are a few different work arounds like safe mode or installing a 3rd party antivirus to disable the default locks