-e: when you install the plugin or load content on IE which needs an update you get an extra file execution prompt

-tested & repro: Win7/IE10, Win8.1/IE11
-tested & no repro: Win7 FF + Chrome

-repro:
--uninstall plugin
--start IE
--go to http://files.unity3d.com/webplayer_test/WebInstall2/
--select Full (trunk)
--click go
--follow the installer
--NOTICE you get an extra prompt to allow running the UnityWebPlayerUpdate.exe
--also notice that two UnityWebPlayerUpdate.exe will stay active in TaskManager