I think I have found the solution to this problem, as I had the same Disk 2 error on my win10 machine. I managed to install the mod successfully after renaming the part 2 file to the exact filename the installer asks for when asking for disk 2.
It appears that the links I downloaded for the "full" 8.0 install are just part 1 of the package as per Leonardo's suggested download site. So I downloaded the two seperate parts from Mod DB. 1,953,125 kb for part 1; 993,162 kb for part 2. I extracted part 1 and 2, ran the installer (part 1, an .exe) and pointed it to my Empire folder in steam. The install began. When it asked for CD 2, I chose "browse folders". I chose an option on the lower right hand corner "Show all files" and navigate to the place I extracted, or unzipped, part 2. I saw the file, but it was not the same filename that the installer was looking for. The installer is looking for a filename that is displayed on the bottom of the "browse folders" window when it asks you for disk 2. I highlighted this filename, right click and copy. Then I went to the folder, in a different window, where part 2 was extracted, or unzipped, and renamed the ENTIRE file name to what the installer was asking for. Once I did that, I was able to highlight that file in the installer and continue the installation successfully.
I hope these instructions don't seem too convoluted. I tried to explain it my best.