Well, there is the ".bak" backup saved game and maybe files with the ending ".au1" to ".au5". All those are saved games.
The main reason for the failed checksum (that I know) is that the file got corrupted on the drive, so that the checksum doesn't match after loading it again. Of course there may be other reasons (like the mentioned bad RAM or drive). Does this occur often or was it the first time you encountered this?