Convert username to SID

Hi Guys,

I have a standard ASP page that is on our intranet on which I am using the
request.servervariables("auth_user") variable to return the domain\username
of the user that made the page request. Does anybody know how I can convert
the username into the SID (S-1-5-!!!!) equivilant for it?

If it is any help it is a WIn2k3 domain.

Hope you can help

Regards,

Nigel