tell application "Finder"
	set allVolumes to the name of every disk
	repeat with i from 1 to the count of allVolumes
		if item i of allVolumes is not the name of the startup disk then
			-- Uncomment the 2 lines below if you don't want Network drives unmounted.
			-- if item i of allVolumes is not "Network" then
			eject (item i of allVolumes)
			-- end if
		end if
	end repeat
end tell