64 Bit development environment

We need to port an application to a 64 Bit environment. As MSDN subscriber
we could download the XP64 Beta. My Question: If we had an Athlon64 system
and the windows 64 beta, how could we develop a 64 Bit C-Application on this
system? Is there a Visual Studio with 64 Bit extensions available? I didn't
find that in subscriber downloads. Or is it possible to compile 64 Bit code
with the good old VC 7? Or do we really need to install Linux64 to get 64
Bit support...