The easiest way to convert a project/solution created using VS.NET 2003 to VS.NET 2002 is to edit the "solution" and its "corresponding C# project file" manually.

1. After opening the solution file in Notepad, change the "Format version," which would be on the first line, from "8.00" to "7.00." Save the file and close it.
2. Then open the corresponding C# project file and replace the existing "ProductVersion" and "SchemaVersion" with what's below:

   ProductVersion = "7.0.9466"
   SchemaVersion = "1.0"

   Save and close the file.