When installing Lync server 2013 this error bugged me.
What could be wrong. with SqlExpress? Tried installing “sqlexpr_64.exe” from the DVD and here is my problem.
Something went wrong when I downloaded the ISO image. Deleted the downloaded imaged and did a new download. After mounting the image I ran setup.exe and the same error appeared. I then remembered that Lync setup copies setup files to the cache. Deleted Lync setup cache directory from “C:\ProgramData\Microsoft\Lync Server\Deployment”. After this the install ran perfectly.