Can I distinguish between compiled application from VS2008 Professional and Express?

+5  A: 

No. The same compiler is used by both. The main difference is in the tool set included with Visual Studio, not the compiler.

Reed Copsey
+1. Beat me to the punch.
David Stratton
+1  A: 

No. They both compile down to the same MSIL. You are free to make, sell, and distribute applications written in the Express versions. The difference is not in what the products produce, but in the tools that you have at your disposal. The Professional version just gives you more bells and whistles, and makes development easier.

David Stratton
Visual Studio doesn't always compile into MSIL (ie: if you're using native C++), but otherwise, your answer is true.
Reed Copsey
Good point. I hadn't thought of that.
David Stratton