Diagnosing problem with running ASP.NET app as 64-bit

I need to run an ASP.NET app as 64-bit. The app is quite large and has MANY assemblies to load. When I run it I am getting "is not a valid Win32 application" error in the web page as soon as I go to 开发者_JAVA技巧the first page. That page is a very simple "Hello World" page. However, it must be having problem with loading assemblies as 64-bit. How can I figure out which one(s) are the problem?

When you say "run as 64-bit" do you mean you are running on Windows 2008 x64/IIS 7? Also if you are having trouble running an app that worked fine on the 32-bit flavor, you can use CorFlags to specifically tell your assemblies to run in 32 bit mode on a x64 machine. This came very handy on our new Citrix farm which was all Win2k8 64-bit, we had a lot of vendor .net apps behave strangely/not work at all, until we discovered this tool

are you running IIS in 64 bit mode? http://blog.danbartels.com/archive/2005/05/18/662.aspx