When that happens, to uninstall the game, you need to manually delete the Cyan Worlds folder from your system. It should be located in your C:\Program Files\Ubisoft folder. Once that is done, you must also delete the vpd.properties file located in your Windows folder. *Please note* that the vpd.properties file may be in use by another program installed on your PC. Before deleting this file, you may want to edit it with Notepad to see if there are any other programs mentioned in the file. If Myst V is the only program using this file, it is safe to delete. If there is mention of another program in this file, just remove the lines pertaining to Myst V.