That it booted as far as it did without crashing. when changing a MOBO/CPU one must take steps to avoid the OS from taking such a jolt, XP is very sensitive to big changes due to licenseing requirements.with all that said the best way I have found is to do a repair install, I have tried other methods but none have

Move HDD to an all new system or change MOBO/CPU in existing System.

1=After the hardware is changed Use "Repair Install" procedure, be sure the system is booting from the cd/rom drive and the full insatll OS/CD is in the drive.Do not allow the computer to boot from the HDD.
2=After the repair the system may freeze at or before the desktop, just manually re-boot.
3=Install new MOBO drivers, and any other drivers you may need..
4=You may have to clean up the Device manager and User Accounts
5=You will need the product key.
5=You will need to re-activate.

Repair Install

NOTE: A Repair Install will replace the system files with the files on the XP CD that is used for the Repair Install. It will leave your applications and settings intact, but Windows updates will need to be reapplied.
NOTE: Factory supplied Restore Disks will not work to do a Repair Install.

NOTE: If possible, Before doing the rapair install copy the wpa.dbl file to a floppy and after the repair copy/paste the file to the C:\windows\system32 folder, This will save doing a re-activation of the OS. works only if no hardware changes are made.

1=Set BIOS to boot from the CD/ROM.
2=If the prompt to "Press any key to boot from CD/ROM appears (it should not on a repair Install)(Do so now as you have only seconds).(Ignore if prompt appears on any reboot)
3=Windows setup, Loads files.
4=You will see Windows XP home or Pro setup.
5=To setup windows press "Enter."
6=Press F8 to accept license.
7=To repair selected Windows Installation press "R."
8=Copies files to the Hard drive. 9=Computer will re-boot--Do not use the use the "press any key" command at the prompt.
10=follow the on-screen instructions..
11=Enter the "product Key" (Note- It is possible to enter a different product key from the one that was used to install the OS you are repairing but you will run into Licensing problems with MS.
12=The computer may re-boot again during the install, but do not use "the press any key" command at the prompt or you get to do it all over again.
13=Follow on screen instructions.