If you have a previous version (e.g., AutoCAD 2012 or 2013), uninstall it first. Conflicting registry keys can break the AutoCAD 2015 install.
Once you have the installer (e.g., AutoCAD_2015_English_64bit_dlm.sfx.exe), follow these steps exactly. autocad 2015 install
After installation, you may encounter these issues: If you have a previous version (e