Best Answer Vainamoinen , 03 September 2016 - 01:14
So, this is the error message on GOG when I double click on the set-up for 'part 1 of 4.'
"Installer files missing - please make sure you have downloaded all necessary parts. You will be asked for their location during installation. Integrity check will be skipped."
Okay, of course the first thing to check is that you indeed did download all the parts, that they're the correct parts as well, and that they have the correct names so that the installer finds them. At the time, the GOG download indeed has four parts which should be downloaded to the same directory.
If all that is the case and the problem persists: It's strange that the installer says that parts are missing if they in fact aren't, but the only reason for this that I can think of is file corruption. So maybe deleting and redownloading individual parts may help...? Go to the full post