Let's say I bought a game on retail or another digital, non-Steam download and installed it on my hard drive. I buy the same game (or a minor variant of it, say the GOTY edition) on Steam. It should be possible to use the existing installation to avoid the generally large downloads. This is very useful, as it saves both bandwidth and time.
Previously, as far as I understood, Steam downloaded the game files directly to
steam\steamapps\common\<game_name>. Since this folder would be created on starting the download, pausing and closing Steam, copying the game files to this folder, and then validating the game files would make Steam absorb as much as possible and just download the missing files.
Currently, Steam downloads the files to
steam\steamapps\downloading\<game_id> and then moves them over to the aforementioned folder once the download finishes. So first of all, what the final folder would be is not clear. So what would be the correct way of doing the same thing, that is, making Steam use as much of the existing files as possible? Should the files be copied to
downloading\*\, or should I figure out the actual folder (say via googling) and copy the files to
More specifically, I had a retail copy of Arkham City installed, and I just bought the GOTY version on Steam. Now I tried both of the above things, in either case, the validating does not seem to do anything. Assuming I have the correct folder name,
steamapps\common\Batman Arkham City GOTY, according to this, if I copy the files there, Steam seems to just continue with its 17GB download. If I copy it to
steamapps\downloading\200260, then the download keeps stopping every few seconds with "Disk Write Error" after modifying 1 or 2 files, and I have to keep hitting resume.