SQL 2008 R2 Express Setup on Win8 triggers Program Compatibility Wizard, but not on another Win8 box

I've been tasked with trying to solve a mystery.  We have two Windows 8 systems that we are installing SQL 2008 Express R2 on.  One installed without incident, the other triggers the Program Comptability Assistant.  Since we want to perform our installs silently, having the PCA come up is going to be a problem.  What I want to know is roughly when SQL 2008 R2 setup was added to the PCA.