There is no difference in project files (.vcproj) except the version number, you can easily open projects created with VS2005 in VS.NET 2003 by modyfing the version number of the project using the text editor.

Unfortunately, solution files (.sln) in VS2005 and VS.NET 2003 have different formats and there is no utilities available to convert solution files from VS2005 to VS.NET 2003 format. So you must create a new solution in VS.NET 2003 and then add converted projects.

Here is an instruction how you can do this.

1. Open the project file (.vcproj) in any text editor like Notepad.
2. Change Version=”8.00″ to Version=”7.10″.
3. Save the file.
4. Add the project to a new VS.NET 2003 solution.
5. Build the solution.