Performance issue for TCP server application in win 2003 server

[Maliron]

I have a program with a TCP server in a Windows 2000 professional. I
the test performance of this program with an other program

with a TCP client. In the the Windows 2000 the performace of the the
TCP server program is OK.

For example with 1000 clients there is no impact to the TCP servers
latency or to the CPU.

When I move the TCP server to Windows 2003 server, the performance
decreases significantly. I get very high latency already with

300-400 clients, but with no impact to the servers CPU. Already with
one client in the Windows 2003 the latency is 4 times

greater, than in the Windows 2000.

Any ideas how I can get the system working in Windows 2003 server as
good as in the Windows 2000?