Take note when you install SP2 for Windows XP, it will actually put a cap on the number of simultaneous TCP connections your OS can make. This does not bode well for those who running peer-peer software or multiple networking applications together.
Use the following registry script, save it as TcpNumConnections.reg, and merge it into your registryWindows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
"TcpNumConnections"=dword:00fffffe