This all might sound confusing and I apologize if it is. But on GOG.com there are backups of The Witcher 1 and 2 that are completely DRM free. I am paranoid and downloaded the Witcher 1 backup just in case and now have all of the files for the game. If I wanted to install the game all I'd have to do is run the exe right?
you run the installer that gog make for each game. the backup should be placed on a separate drive preferably 1 you dont constantly write to to reduce the chance of file corruption. other than that you should ave no issues installing the game from the files you downloaded. gog do a lot of re-releases all of which are drm free. i recommend them highly, $5-$10 for classics is a bargain. especially when they can appear on steam and origin at more than x2 the price with there drm intact.