Today I spent about 4 hours attempting to get an MVC2 application working under IIS6 on a windows server 2003 machine, only to end up with 404 errors where ever I turned – until a co-worker finally had a brain wave and said that I had to do something special in IIS to make sure routing works.
After stumbling across this post http://mvchosting.asphostcentral.com/post/ASPHostCentralcom-Hosting-and-Deployment-of-an-ASPNET-MVC-Application-in-IIS6-and-IIS7.aspx I got my asp.net app working in under 5 minutes.