Sometimes Windows Installer will pile up a queue of items to be installed. These will show up as multiple ‘msiexec’ processes in TASKMGR. To clear them:
msiexec /unregister taskkill /f /im msiexec.exe msiexec /regserver
The idea is, first we take Windows Installer offline, then we kill any leftover stalled / queued processes, and lastly, we bring Windows Installer online again. Unless there’s something else in the backgrounds starting more of these things, this will take good care.