To install WinRats 8.x from Estima silently on windows systems use:

msiexec /i “WinRATSStd800.msi” /qn /norestart ALLUSERS=2 PIDKEY=”???###” AGREETOLICENSE=2 ORGANIZATION=”Your company name”

For more information see:
http://www.appdeploy.com/packages/detail.asp?id=2248