Start-Run: regedit- Enter the registry
1. Start-Run-Enter "regedit", open the registry and find the following registry path:
HKEY _ LOCAL _ MACHINE \ SOFTWARE \ Autodesk \ AutoCAD \ r 18.0
Right mouse button to delete the entire key value R 18.0.
2. Find the following registry path:
HKEY _ Current _ User \ Software \Autodesk\AutoCAD\R 18.0
Right mouse button to delete the entire key value R 18.0.
3. The last and most important step is to find the following registry path:
Under HKEY Local Machine \ Software \ Class \ Installer \ Product,
Click the right mouse button to delete the key value at the beginning of "7D2F3875 1008xxxxx".
Then you can reinstall it.