Just use the 2005 express, you're not missing out on much unless you plan on doing some ASP.NET / ADO.NET. Knowing Microsoft's track record, 05 will be delayed :P.
IMO it's not worth it to buy 2003 right now -> You might be better off sticking with 2005 express if you already have it. If you have 2002...that might be a problem when working in groups, but this issue can easily be resolved with a "Source code type converter."
One more thing, if MS doesn't allow .NET Framework 2.0 support for 2002/2003, then I' d get 2005.
-TPG