To anyone having problems with the KeyGen during install: make sure you run AutoCAD as the administrator (either right-click and Run As Admin, or right-click, Properties, Security, select Run As Admin). Also make sure you run the correct KeyGen as the admin. Also, copy your Reference Code to the KeyGen(from the A/CAD licence window), then click Patch, then Generate. Copy the new key into A/CAD. It should work.