The existing file is being used by Windows and cannot be modified. In case you are installing the new version of YeetDL in the same location as the previous one, make sure to close any instances of YeetDL that are running before installing a new version which, in normal cases, our installer will do automatically. In case the issue persists, uninstall the older version of YeetDL by using 'Add or Remove Programs' in the Windows Control Panel and the install the latest version.