Error 1500 Another installation is on progress. you must complete that installation before continuing this one.
Well - obviously there’s some unfinished installation happening there, as the message clearly and unambiguously indicates. If you don’t see it, it must be something in background, possibly stalled/hung from your previous installations, or from some component automatic updater. If in doubt, just reboot and retry.
This happened to me when I was updating LibreOffice. I do not know why the update failed, but it may have been because I was running a few programmes that were consuming a huge chunk of CPU processing. In any case, even though the update failed, Windows installer was still running after the failure, preventing me from retrying.
Rebooting the machine is a simple way to solve this. Another way is to locate in Task Manager the Windows Installer that is running, and end the process there.