http://support.microsoft.com/default...;en-us;Q316401 SYMPTOMS
When you start your Microsoft Windows XP-based computer after you replace the motherboard on the computer, you may receive a Stop error message that is similar to the following: STOP 0x0000007B INACCESSABLE_BOOT_DEVICE
CAUSE
This issue may occur if the new motherboard contains an embedded IDE controller that has a different chipset than the original motherboard.
RESOLUTION
To resolve this issue, use one of the following methods.
Method 1: Perform an in-place upgrade of Windows XP
If the old IDE controller and the new IDE controller detected your hard disk as the same size, perform an in-place upgrade of Windows XP.
How to perform an in-place upgrade (reinstallation) of Windows XP :
http://support.microsoft.com/kb/315341/ Method 2: Repartition and format your hard disk and reinstall Windows XP
If the new IDE controller detected a different size for your hard disk, you must repartition and format your hard disk, and then reinstall Windows XP.
How to partition and format a hard disk in Windows XP
http://support.microsoft.com/kb/313348/