can't change "setq tex-dvi-view-command"

[Paminu]

I use emacs and auctex in cygwin for winXP.

I have this in my .emacs file:

(setq tex-dvi-view-command "start_xdvi")

I have made a bat file called start_xdvi that opens xdvi and a xserver. I 
works fine if I type "start_xdvi" from Run.

But when I want to use the default viewer by pressing C-c C-c it just uses 
the comand :

View command: xdvi -sourceposition "18 formelsamling.tex" -editor 
"emacsclient --no-wait +%l %f" formelsamling.dvi

why does it not uses "start_xdvi" instead when I have specified it in my 
.emacs file?