MsiInstallProduct credentials

Hello,

I've built an MSI installer with Installshield that has an updated executable and a few other bits inside it that I need to run from within an MFC C++ executable.  I want to use MsiInstallProduct to grab the MSI from our web server and run it.

I put the MSI in C:\inetpub\wwwroot\installer\update.msi  running on IIS 7.5.7600.16385

Authentication on that directory where the installer sits is Windows Authentication - enabled, every other kind - disabled.

When I call MsiInstallProduct and pass the path to the installer, I get a 401 in the W3SVC1 log

		installerName += pDelivery->GetServerName();
		installerName += _T("/Installer/");
		installerName += newVersion + _T(".msi");

		UINT ret = MsiInstallProduct(installerName.c_str(), "");

Is there a way to pass username and password so the call to MsiInstallProduct will hand those to IIS and work with Windows Authentication?

Currently I have to enable Anonymous Authentication to get it working.  

Thanks for any help!