.msb files are files that contain various messages, in compiled form. For those who might be interesting in getting it unpacked, here is my utility with source code intended to unpack error numbers and messages from these files.
Download win32 binary + source code.
I also added a section to my "Reverse Engineering for Beginners" book about file format details.
→ [list of blog posts] Please drop me email about bug(s) and/or suggestion(s): my emails.