Changing User running PHP script under IIS7

[php@xxxxxxxxxxxxxx]

Hello.

I need a little help with setting up php with IIS and in particular to set
the user running PHP so far I just found nothing the anonymous
authentification is active and defined to the specific user but it don't
seem that PHP is running with that user. the script are launched by the
NETWORK SERVICe which can't do what I require it to do as it needs better
rights for running an external program that has to set acl and
unfortunately I can't seem to get php using the user I want as it fails.

Best Regards.

Aurelien