Shortly after uninstalling cad20 10, cad20 10 was installed, but the last step said that "another version of cad already exists in the target directory"
Didn't the installation succeed? If you install it on disk E, it also imports some applications to disk C. It is suggested that you manually delete the installation files installed on other disks (disk D, disk E and disk F) after uninstalling. When uninstalling, only drive C is uninstalled.