If the receive buffer is too small on Windows XP, it might cause your internet connection to be unusually slow.
To fix that you need to increase the receive buffer size, as follows:
Start > Run
In the run dialog type regedit, then click OK
In registry editor select: HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParameters
Do: Edit > New > DWORD Value
Name the new key: TcpWindowSize
Double click to edit the value
Change the Base Setting to Decimal
Set the value to 64240
Exit regedit and restart your computer