I just purchased Serum and Cthulu, and downloaded the Windows installers. I notice that the files don't have any file extension for some reason? I tried to set an extension of .msi, .zip, and then finally found that they're actually .exe files. The same behavior was on different PC's (each with different Anti-Virus software, so I don't think it's the AV software that's removing the extensions). Anyway, I got things working after I set these to .exe files, but I'm not sure why the file extensions were missing.