Tuck;
Is it OEM or Retail Windows XP?
If Retail, a Repair Installation may be required to properly detect
the new hardware:
Repair Installation:
http://www.dougknox.com/xp/tips/xp_repair_install.htm
Windows Updates will need to be reinstalled.
Data should be safe, back-up important data just in case.
Install Service Pack first and by itself.
Then install ALL Critical Updates no more than 4 at a time,
Disconnect the network/modem cable before starting repair and do NOT
reconnect the cable until repair is completed and firewall is
installed/enabled.
http://support.microsoft.com/?kbid=283673
If OEM, did Windows XP come with the computer?
If so, you may not be able to, contact the computer manufacturer for
details.