It is normal that the My Documents D:OS folder remains. You can just leave it as-is, or rename/move the folder, and the game will recreate it the next time it is started, and prompt you to create a new profile. In the latter case, once you get the game working, you could either delete the new D:OS folder and rename the original folder back again, or just move the saves from the old profile's savegames folder to the new one.
If you've uninstalled the game, it would be safe to delete the install folder (or just any remaining contents), maybe reboot and shut down all non-essential programs, and then re-install the game.
It would probably be easiest to leave the The My Documents folder as it is, and just try to rename/move it if the clean re-install doesn't get rid of the error.
