Capt.Jack Sparrow said:
What i used to do in these situation would to change the extension of that file copy it to a location where noone would suspect even if they suspect without know what file is it they can't open it.
Ex. If you have a Word document SevenForum.docx change the File name and extension to something else like DataFile.zip so even if they double click it would say that Zip file is corrupt. This is the same process these Encryption program do but they hide it as well

Hope this helps
Captain
I would not do that trick with a .docx file, remember that, the file is stored in Microsoft XML and double clicking on (DataFile.zip) will open the XML structure.