Solidworks API SDK

I've DL'd the API SDK from the solidworks site and installed it.
I am getting the application wizards to work to load up the
appropriate code, but in the code I get many compilation errors.
I am currently using SW+2001, and VS.net 2002. I am trying to do a C#
application. In the header of the C# pre-built app, it says that the
files
sldworks.tlb, swconst.tlb and swpublished.tlb must be manually added.
I do not have swconst.tlb (but I found a swconst.cs file and simply
added it to the project which seemed to fix some of the problems) and
some of the other code seems to use newer function calls, for example
the call: iSwApp.AddToolbar4 is not defined.

My main question(s) is/(are) this:
Is there an API SDK for SW+2001?
If I migrated to SW2003 would these issues be resolved, or does 2003
have it's own API SDK I can install?
Am I forced to use SW2004? Currently the SW group uses 2003, and I do
not know when they will move to 2004.

Thanks for any assistance
~Sinisa