Unless you saved a backup copy you may not be able to. Notepad is a VERY basic text editor. It does not have a lot of features like Word or other editors that may save a backup copy automatically. If you are restoring an older version, check to make sure the date / time on the file is indeed an older version. For a text file that you are editing on a regular basis you way want to use a different editor and consider adding a version number or timestamp to the file name to keep multiple versions in case you need to rollback the data.