Recently, I got this message during DPM installation : “Another installation is already in progress”. But there was definitely no other installation in progress on my 2012 server.
Go to “services.msc” and confirm that “Windows Installer” is running all the time (even if you reboot your server)
I solved my issue :
1/ Kill the “Windows Installer” process in your Task Manager
2/ After that, I was able to stop the “Windows Installer” service