I'm thinking of making a program that will check (based on MD5 checksums) what version of SS2 the user has; so my question is what is a reliable file to run a checksum on in order to determine what version of the program the user has installed?

Thanks.

There is official patch 2.3, NewDark 2.4 and 2.41 and that's about it. Checking exe file will determine which is it. Older versions AFAIK would not even run on modern OS. I don't think that information what user has installed could be presented as one number because there are additional dll files that could be in different versions, game might be mod ready or not mod ready and so on. Exe file version number doesn't say too much.