I've tried to download the following: Heroes of the Lance, Dragons of Flame, Shadow Sorcerer and War of the Lance. I've tried everything in my power to fix it, but I always get the same result: Installation failed. Is there really a problem with the installation, or is there a bug? Thanks in advance.

Works for me.

Do you try to install the games with GOG Galaxy or manually with installers? If you use Galaxy, do you have enough free space on the drive you are trying to install the games to, and do you have enough free space on the drive Galaxy downloads the files to?

Nevermind. I just had to uninstall the outdated Galaxy client with the updated one, and the aforementioned games were downloaded without any problems whatsoever.