..wbk files are Word Backup Files. When you have the option to always save a
backup copy set (see Tools > Options > Save tab) Word will save a copy of
the last saved version of the file as "Backup of whatever.wbk". The files
are, however, not encrypted (unless the originals were).
I don't know why you would be e-mailing these out - perhaps SHOUTING at the
computer made it misbehave! How are you sending the documents?
