Slow file copy after about 1GB to server OS

I've read through this article and spent 3 days troubleshooting;
http://groups.google.com/group/micro...dcb103467382cc

We've got requiresecuritysignature set to 0 and we've played with
various settings on TcpDelAckTicks. No difference.

If we take two XP PRO PC's and hook them up back to back, we can
transfer many many GB files at full speed (about 35MB/s, hard drive
write speed limit.)

If we take the same file to the servers, they run at full speed
(Around 50MB/s) for about the first 1GB of data, then then switch to
about 3-5MB/s for the rest of the transfer.

This is repeatable on HP Netserver, Compaq Proliant, SuperMicro so
it's not server hardware specific. If we remove all software
including antivirus and just have a Windows server with a cross over
cable to the workstation which can drive another XP PRO workstation
with no problems -- when crossed over with the server the problem of
slowness persists.

So it's not the Network and it's not 3rd party software. No 3rd party
software installed.

In my mind this means the problem has to be within the OS itself.
This affects Windows 2000 server standard with SP4 and fully patched,
as well as Windows 2003 SP1. This has been occurring for at least 2
months.

If I do the same tests to Samba or other non Windows servers, I don't
have the problem either.

What settings do I need to look at? Is this a *feature*? If so, how
do I disable it? We have backup servers where we copy huge images
(Ghost, True Image, etc) and we need to get our throughput up.

Thanks;

Edwin