Well I Can tell you that adding hardware is similar to that of windows 9x but in XP there is an option if you look at any device to "Roll Back Driver" if the card exists and those dogy dialers might have updated the drivers to some dogy one that does not work.
failing that DO NOT USE SYSTEM RESTORE as i have found it makes life worse (in XP anyway) just remove the cards drivers and pull out the sound card (suggesting it is not onboard if it is then simply remove drivers) and plug it in again bott the system up and it should detect the card and you have to tell it where the drivers are like X:\drivers\winxp (something like that x being your CD drive letter mine is Q)
i hope this helps!
from stuntmaster. (ben)