emacsclient uses obsolete "server" file on Windows

[djc]

My _emacs contains

    (require 'server)
    (server-start)

When I kill emacs the "server" file remains. As a result, when I first invoke

    \path\emacsclientw.exe -a \path\runemacs.exe FILE

emacsclientw finds the obsolete "server" file, tries to use the information 
in it, and blocks with an error message saying the server has refused 
connection. (Actually, of course, the server doesn't exist.) Once I click 
to dismiss the message, everything proceeds fine: emacsclientw invokes 
runemacs, which starts emacs on the file. emacs writes a new, valid 
"server" file so further invoking the same command line works properly. It 
also works properly when there is no "server" file.

This can't possibly be how things are supposed to go. How should things be 
set up so the command above will always work without blocking? Hook 
deleting the file to "kill-emacs"?

I'm new to emacsclient after using gnuclient/gnuserv for years, so perhaps 
I've missed something obvious. If so, just point it out.  Thanks.

Pete