Peter,
The default 'name' that is used to sort the files in the contacts directory
is the 'file name'.
The contacts are stored one contact per file in the contacts directory,
rather than entries in a single data base file. Each file has an extension
of .contacts so that the system knows how to handle that file. You can
change the file extension to something else or open the file with some other
program (rather than the default 'windows contacts' and examine the contents
(look at one with notepad for instance). You could also have a .contacts
file anywhere in your system and it would open in the 'windows contacts'
program by default.
If you would actually like to sort by first name or last name, rather than
file name, you can do so by adding those columns to the display.
Personally I am rather impressed that MS was able to radically change to
structure of the 'windows address book' (*.wab file and wab program) and
still keep things working for programs that think .wab still exists!
Michael