Install fails - "IIS not installed..."

[mhsi Profile]

Hello, I'm attempting to install the free version (Helicon_Ape_0124_Free.msi) onto virtual Windows 2003 32bit instance running IIS6. Configured install using default install path, Server (full), and Register APE for entire IIS Server checked. I get the error "Error! IIS not installed on your machine. Please install IIS and restart Helicon Ape installation." - but IIS is installed, running, and serving sites. Any help troubleshooting this would be appreciated.