TS 7.3.2 Install on Win 2008 R2 Server prompts for IIS User

System

Previously, IIS ran as IUSR_ and with the new version of IIS (7) that comes with Windows 2008 R2 server it now, supposedly, runs as just IUSR. As such, when the TS 7.3.2 installer runs it prompts for IIS user and password. I have tried IUSR with no password (what MS says it uses / needs) and it does not work. I have tried IUSR_ and it doesn't work. What are you supposed to supply here?

Windows 2008 R2 server 64 bit.
TeamSite 7.3.2