Connection speed issues - Window Scaling ?

Hi all,
I have a network, connection speed issue with a Windows 2003 standard
server.
The problem is HTTP and FTP download speeds from remote machines.
Basically the connection starts off ok and then within a couple of seconds
it reduces to approximatly 40k/s. This happens from any location, a
traceroute shows no problems with the network, its basically being capped by
the server itself.

I have other servers on the same connection and they do not have this speed
issue.

I am told (by a datacentre technician that provides our hardware and
connectivity) that the issue is not related to hardware, but to the TCP
stack on the server. It is setting the Window Scaling TCP option to 0, which
limits max TCP window size to 65K. Alterations to the registry to affect
the TCP options are having no effect, so we are unable to readily identify
exactly what on the servers is causing the issue.

Anyone have any ideas what could cause this? or how i go about starting to
find out the cause of it?

Many thanks.