Splunk 7.3.1 is not supported on Windows Server 2003.
Windows Server 2003 is discontinued.
I know its not supported, but its trying to install on our old 2003 servers. When you run the MSI it aborts as the OS is unsupported which is fine, but the PatchMyPC detection rule obviously includes 2003 when it shouldn't.
We are using a rule to detect OSes starting from Server 2008 in today's update for v7.3.1.1
Not sure why we missed it in the previous one! Sorry about that.