When installing VS 2015, the installer was interrupted and the process was terminated. Later I successfully ran the installer again. However, the program won't start. Clicking the icon does nothing. I tried running 'devenv.exe' manually and got this message:
Program 'devenv.exe' failed to run: The application has failed to start because its side-by-side configuration is incorrect. Please see the application event log or use the command-line sxstrace.exe tool for more detailAt line:1 char:1
Using sxstrace.exe, I got the log, which is huge. Notably, this appears multiple times:
INFO: Did not find the assembly in WinSxS.
and it ends with this message:
ERROR: Cannot resolve reference coloader80.dll,processorArchitecture="X86",type="win32",version="1.0.0.0".
I have tried repairing the installation as well as uninstalling/reinstalling. I also tried a forced uninstall ([installer_file] /uninstall /force).
I'm using the web installer.
The problem was a broken Visual C++ Redistributable 2015 installation, resulting from the interrupted setup. Visual C++ Redistributable 2015 was not shown in Programs and Features, so there was no way to uninstall it, or even know that it was installed. But VS 2015 setup was apparently assuming it was installed.
I used this tool to find and uninstall Visual C++ Redistributable 2015. I then fore-uninstalled VS 2015 and reinstalled it (possibly after a restart).
I also uninstalled all other versions of Visual C++ Redistributable that were shown by windows, but this was perhaps unnecessary. Later I repaired VS 2017, so that Visual C++ Redistributable 2017 was installed as well.
Now both VS 2017 and VS 2015 are working.