Dr.TCP is a simple but powerful utility that can let you fine tune the TCP/IP parameters for your Network Interface Card (NIC). It works on Windows XP, 2003,2000.
Dr.TCP takes the hassle out of editing the Windows Registry and modifying keys to fine tune the TCP/IP Parameters at
[HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\<AdapterID>]
Although, this is easy to use, it takes a bit of understanding of TCP/IP protocol stack to know what each of the parameters do.
The utility can set or modify the following on a per interface basis
Set MTU (Maximum Transmission Unit)
TCP Receive windowEnable/Disable Path MTU Discovery
Enable/Disable Blackhole router detection
Enable/Disable Window Scaling
Enable/Disable Time Stamp
Enable/Disable SACK (Select ACK)
Set Maximum Duplicate ACKs
Set TTL (Time To Live)
To download the tool, click here