MapVirtualKey returning 0

Hi,
Does anyone know when MapVirtualKey returns 0, meaning there is no translation for the provided scan code, how else we can get the virtual key for a particular scan code?
This is a non-standard key that I'm trying to find its virtual key and running an app called KeyboardTest shows that its Windows Key code is 0xff.
Any other keys (even non-standard) with a Windows Key code other than 0xff does get mapped successfully with this call.
Any help will be appreciated.
Thanks.