the modem in that laptop is the conexant HD smart modem is cp
as long as you have got the sound running the driver for the modem should come from windows update.
go in to device manager, right click on the modem, and select update driver.
let windows auto search and tell it search online as well, that way it will search windows update for the driver.
if that fails to work the most up to date driver direct from microsoft is version 220.127.116.11 dated, 11/5/2008
you can find that driver on the bottom of this post,
please fully unpack that driver with winzip
you will have to force xp to accept this driver by using the new hardware wizard, then let it auto choose the modem, click have disk and point it to the fully unpacked driver.