Not sure if it will help, but IIRC, there were lots of defective installer disks with LE8 and MP 8(as long as you registered it, you could probably get a fresh download from your MyAvid account). In any case, you need to open the disk(or download), find the Setup file, right-click on it and choose Run as Administrator(which actually should be done for any software install on Win7 or 10). You will likely also need the 8.0.5 updater(run as admin after you restart from the original install).
Having said that, what happened with the previous system drive? If it was working well, a disk clone might save a lot of hassle
