ASP.Net in Xamarin Studio 64-bit

I am unable to run my ASP.Net MVC project in Xamarin Studio on Windows 7, but it works fine on a Mac OS.

This is the error I get on Xamarin / Win7.

System.Runtime.InteropServices.COMException (0x80070032): The request is not supported. 

I found out that this is because Mac OS targets 32-bit architecture by default, and the Xamarin debugger does not support 64-bit processes.

How do I set my Xamarin Studio on Windows 7 to also target 32-bit instead of 64-bit?