on x64 Windows 7 I am trying to get hello world MVC 3 website running as 64-bit process (so Environment.Is64BitProcess returns true on a page) using IIS Express 8 latest bet
Simple possibility is just to set IIS x64 as starting program for the WEB project :
Project Properties -> Web -> Start Action - > Start Program : c:\Program Files\IIS Express\iisexpress.exe command arguments: /path:{yourProjectPath} /port:{yourPort}