Download one thread of text How do I select one string of text messages and download to PC so that I can print?  I've tried downloading and it provides a .hbk file which I can not open.  I don't even know where to look on my HTC to look for my SMS card file information to convert to something else.
.hbk is HTC messages backup extension: you can "write" them only via backup from phone and "read" only via the restore option. 
See  this for more information about how to open or write these files