Windows XP has optimized the network speed enough.
However, you can add some Network speed to your connection by disabling some unusing network items. You can absolutely safe disable:
QoS Packet Scheduler - this item is of no use in most home environments.
File and Printer Sharing for Microsoft Networks - if you have not shared files or printers in network - disable it.
Also you can add some network speed using WinTools.net tweaks.
Go to Net Tweak tool.
Press Use optimum settings for a selected configuration.
Select suitable importance for your connection, for example: LAN, Cable Modem, xDSL, ISDN, T1, etc.
And press Apply button.
Note: You can restore your network setting using the option of MS Windows default Internet and Network configuration.