I had this problem this morning and got to the bottom of the cause through reading this thread. The error in my log file said it couldn't find the installation files for my version of SQL Express 2012 so I searched for it and downloaded a copy. When I ran the install file it came up with a pop-up part way through saying it couldn't find the source of my original install file for the copy that was already installed on my machine. It turned out that I had installed a version of SQL Express 2012 from an image file for another software package and I had since removed from my machine. I copied the install files back and pointed to the file it was asking for and hey presto. Once I'd done that I was then able to install WinCC Flexible 2005 SP5 without any problems.

AutoGen_1055159

This is why Siemens makes life difficult for all.

 I love Siemens, without it it would be boring

Hi

I had the same problem and solved just installing it as local user.