Have you ever found your computer slowing to a crawl when working on the network? That's because WindowsXP by default, uses your CPU to process network tasks instead of off loading them onto the network card which obviously chews up less resources.
Luckily if you have a good network card you can force Windows to do all the calculations at the network card instead of on your processor.
First load up regedit (start -> run then type regedit and press ok). >From there follow this path HKEY_LOCAL_MACHINE -> SYSTEM -> CurrentControlSet -> Services -> Tcpip -> Parameters and find/create the DisableTaskoffload DWORD value. Set its value to 0 then save and reboot.
Once that's done WindowsXP will use your NIC's processing power to handle any network tasks instead of the main processor.