Have you credited the full source code from Codeplex as described here ? If you want to work with a source (for example, to develop a module), you must extract the full source and not use a ready-made package designed for server deployment.
In addition, I would advise you to read this article about creating Orchard from a source. Visual Web Developer 2010 Express should work fine (since Orchard can be built without VS at all).
Itβs good that the .proj file was not recognized - itβs just an MSBuild XML file to automate the build process. You almost never have to touch them.
Piotr szmyd
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