geeez, Sharepoint community, if you want to use and to install Powerpivot for Sharepoint (which is a superb product,by the way) on the IW VPC that Microsoft provides as I tried to do this afternoon (I wasted at least 4 hours, yes 4!!!), READ THIS POST from a member of the Powerpivot team (Dave Wickert
If you don’t do that, you will get the following error message during the setup :
…and you will have to remove the installed files : I will save your day again by providing the official uninstall procedure here.
…and don’t forget to deploy the powerpivotwebapps.wsp to your web application (in Central Admin-System settings-Manage Farm Solutions).
At the time of this writing this was not clear…
You can also find the PowerPivot for Sharepoint forums here.