Same problem here. Any ideas? There is a "install sql 2016.txt" file in the scripts directory that has "/INSTANCEDIR="C:\Program Files\Microsoft SQL Server" in it. So I assume this is where its getting C: from, but I cannot see any reference to it in the .ps1 file...... wierd. Going to do a manual install for now as it seems SQL didnt install correctly anyway. I only have SQL Client Connectivity SDK install when i try to uninstall. And it wont let me uninstall it which is rather annoying.