Get your Windows XP CD out & ready. Due to the change in motherboard & processor and due to the way Windows XP handles access to hardware devices, you will have to do a repair-install of Windows XP.
Be sure to have your XP CD handy, and even better, if your system is XP with Service Pack 2, then:
1) either have a slipstream copy of XP with SP2
or 2) your XP CD already contains Service Pack 2.
Following is the Repair Install scenario.
Only if you have a "full" XP CD ----
The object of this exercise is to do an in-place upgrade or an in-place installation for purposes of "repair".
It needs to go to the same partition as before , and the same directory as before.
Usually for example XP is on C drive and is on folder/directory \Windows or \WINNT.
Configure your computer to start from the CD-ROM drive. You do that from the pc BIOS setup screen. You specify CDROM as the first drive to boot from.
Insert your Windows XP CD into your CD-ROM drive, and then restart your pc.
When the "Press any key to boot from CD" message is displayed on your
screen, press a key to boot pc from the XP CD.
When you see the following message displayed on the Welcome to Setup screen,
press ENTER:
To setup Windows XP now, press ENTER.
At this point an option to press R to enter the Recovery Console is displayed. Do NOT select this option.
On the Windows XP Licensing Agreement screen, press F8 function key to agree to it.
Make sure that your current installation of Windows XP (in your case, the one you wish to repair) is selected in the box, and then press the R key to repair XP.
Follow the instructions on the screen.