Safe Mode:
Type this in a command prompt and hit Enter:
REG ADD "HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal\MSIServer" /VE /T REG_SZ /F /D "Service"
Then start the Windows Installer service by typing
net start msiserver
References
http://www.thewindowsclub.com/make-windows-installer-work-in-safe-mode