Hello !

Try Googling for a tool called 'project converter' for Visual Studio .NET.
This allows converting .NET solution files into 6.0 workspace files.
Alternatively, you can write code with .NET, test it, and then copy away the
source and header files, generating a new blank workspace with 6.0 and
adding the ready files into the project. This is what I do due to version
differences.

-Antti Keskinen

Also, don't used any "managed extensions" which are new to VC2003.
Write straight C/C++.

--
Sev

.... or :
- turn off the /clr switch
or
- add #pragma unmanaged to every source file in your project

I think this is all ...  take a look in the property panel of your project
and config it the way you need