I have a requirement to install the Microsoft Request Routing component for IIS 7.5 running on a Windows 2008 R2 SP1 64Bit machine.

After installing Microsoft Request Routing via the Web Platform installer our ASP.NET 4.0 application gets a "HTTP Error 503. The service is unavailable."

The Windows event log error details says:

The Module DLL 'C:\Program Files\IIS\Application Request Routing\requestRouter.dll' could not be loaded due to a configuration problem. The current configuration only supports loading images built for a AMD64 processor architecture. The data field contains the error number. To learn more about this issue, including how to troubleshooting this kind of processor architecture mismatch error, see http://go.microsoft.com/fwlink/?LinkId=29349.

I can make this error go away by changing the application pool to run in 32 bit mode by changing the "Enable 32-Bit Applications" setting to true.

However I would prefer not to have to do that to resolve the issue.

My questions are:

1. Why is the Microsoft Request Routing feature trying to load a 32 bit version, isn't there a 64 bit version for it?
2. How do I resolve this issue without having to change my application pool to a 32 bit mode?