Please try the following:-uninstall Corona from the programs and features list-go to disk cleanup in Windows, and clear temporary internet files-open internet explorer and clean browsing cache-Go to your X:\Users\yournamehere\AppData\Local\Autodesk\3dsMax\2015 - 64bit\ENU\en-US\plugcfg\and remove the CoronaRendererMenus.ini file. You may also remove anything else with "Corona" in it if you wish.-In 3ds Max run customize > customize user interface > menus tab > menus at bottom-left > find Corona and delete it (if it's there)-Install Corona againLet me know if that helps or not.The library is installed into C:\Program Files\Corona\materials