Comments by Member 4235983 (Top 1 by date)

As BillHudson explains this is using a feature of NTFS called Alternate Data Streams. (http://www.flexhex.com/docs/articles/alternate-streams.phtml)

Streams from sysinternals will display ADS in files. There is even another Codeproject article explaining ADS at http://www.codeproject.com/KB/shell/csadsdetectorarticle.aspx

This has nothing to do with Notepad. You can add anything (even binary data) in an ADS.