MSVC6.0 disables it's Build System

Hi All,
I have a application that i tried to compile for 64 bit windows
using MSVC++ 6.0 build environment. I started getting some error when i
build using VC++ environment. I uninstalled MSVC and re installed it. After
that i am getting the following message box displayed when i start MSVC.

" No Primary Platforms are available. Build System will be disabled.
It is likely that build system add-on platform (.pkg), installed by setup
failed to load".

I have service pack 6 for MSVC and I am running on Windows 2000.

To me it looks like that i changed some environment settings that i should
not have done.
Any help is highly appriciated,
Thanks,
Ajitabh