I’ve recently had an issue installing legacy software on Server 2019. This legacy software uses IIS 7 or newer.

Server 2019 comes with IIS version 10.

Unfortunately the installer could not pick up that a version newer than 7 was installed. This is due to how it checked the registry to find the version installed.

For fix this, I amended the following Registry value using RegEdit:

ComputerHKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesW3SVCParametersMajorVersion

I changed the value from 10 to 9, ran the installation, then changed it back to 10 afterwards.