1. Open the Registry Editor by typing "regedit" in the Windows 8 Search charm and selecting "regedit" from the Apps section of the search results.
2. Navigate to the "HKEY_LOCAL_MACHINE\Software\Autodesk\AutoCAD\R15.0\ACAD-1:405\AdLM\Type" registry key.
3. Right-click on the registry key and click "Export."
4. Choose a name to save the license registry key file as, along with a location where you want to save it, and then click the "Save" button.
5. In case nothing works, make use of http://www.dwg.openfiletool.com/ DWG Open File Tool