Resume not supported

Hello!

Can someone tell me why my IIS (6.0 installed with Win2003 Standard only
supports HTTP/1.0 and the "Accept-Ranges" entry is not sent in the
POST-Header?
Is that related to version, so only available in Data Center or Enterprise
Edition? Or is it a config switch I can set somewhere?

My problem is that download managers like GetRight or Microsofts own BITS
claim that the server does not support resuming. And really, when I download
something and capture the headers exchanged, everything points to the fact
the server will indeed not support resuming.

Is there something I can do about that?

Thanks a lot for any pointers!
Ralf