Nothing gamebraking, just curious. I have a copy of witcher 2 downloaded at the 4th of July 2013. Recently I downloaded again (12 feb 2015). Noticed a strange thing: even though the versions of the game match (both are of the setup_the_witcher2_ee_3.4.0.25.xxx kind), the size of individual files is different. The recent .exe file is 7KB smaller, the first bin file is 6KB smaller and the last bin file (#11) is almost 50MB bigger (608 vs 562 that the 4/7/2013 file used to be). Also, both installers work ok - its not a case of corrupted d/l.

Since there wasn't a version change, (both appear to be 3.4.0.25) I can't find the reasoning for that discrepancy.

Last few days, I noticed that behaviour in many games, while I was updating my offline GoG games library. Games that have the same version number but the downloader re-d/l them because their size has changed.

Sorry if it has been answered somewhere else, a fast search didn't return with any answer.

PS: It can't be blamed on the file system - all GoG downloads are on the same external drive which always run NTFS.

Basically, it's usually just GOG tweaking the installers. It happens somewhat frequently for some titles, including the Witcher games (in their cases, for all I know, it could be CDPR actually doing the tweaking). For minor fixes and optimizations, I don't think GOG always advance the installer version number, nor do they always bother flagging them with update notifications in users' accounts. (The actual indicator for what specifically was updated on a game that was flagged as updated hasn't worked for ages, anyway.)

If you're interested in keeping abreast of what gets updated, you might want to check in on this thread periodically. It's updated very regularly by user mrkgnao, who wrote a piece of software, MaGog, specifically to keep an eye on the store for when things on the game pages change, or when (for example) game installer file sizes change. One of GOG's staffers, JudasIscariot, also posts there occasionally -- mostly links to update notifications in the various game forums. If you ever have a question on something that was updated recently (or whether something was updated), he'd be a good one to ask.
Unfortunately, I doubt anyone would be able to tell you exactly what had been altered in The Witcher 2 installer files in the year and a half since you previously downloaded it -- it may have been silently updated with these minor tweaks several times in that period -- but as long as the installer version number didn't change, there shouldn't be any worry.

Also, do note that The Witcher 2 has its own separate forum, so if you were searching in this one for updates for the second game, that might be why you didn't find anything. ; ) EDIT: Also, GOG's search functionality is awful, both in the store and in the forums.