Windows Update - Microsoft's guidance if it stops working after XP repair mode
As noted in this earlier entry, the Windows Update process may stop working after performing an XP repair mode restoration from the original CD. Microsoft has just released KB 943144 with instructions on how to register the new Windows Update DLLs to Windows in order to allow the PC to process the 80 or more updates since XP SP2.
Latest Microsoft KB on registering WU process
Some additional blog entries are noted here:
Issues installing updates after repairing XP:
Addressing a Windows Update failure after repairing from XP CD: