This method is valid only under Windows systemes. Becuase Windows cannot read files that have been renamed by DOS using ALT+Number {ASCII Characters}, so when it comes to DOS those files' names are no longer encrypted, and as a result it can be opend readily.
If you have a burning desier to protect your files, there are plenty of file protectors out there. They protect your files by providing a Password for the file. Purchse one an enjoy the Benefits.