what to do after upgrade/replace motherboard - Repair install

Beginners Guides: Upgrading A Motherboard Without Reinstalling - PCSTATS.com

Making windows XP work with new hardware

Unfortunately, swapping out the motherboard is not the end of your toils. Windows really doesn't like having the motherboard changed underneath it, and will generally refuse to boot at all, unless the new motherboard uses the same chipset. No problem. Read on.

Doing a Windows Repair install

To accustom Windows XP to your new hardware, you now need to perform a Windows XP repair install, which redetects all hardware and reinstalls system files without touching the registry or user data present on the system. This process adapts your Windows XP install to the new motherboard it is running on.

To do this insert the Windows CD and restart the PC.
Choose the 'press enter to set up Windows XP now' option.
Press F8 to skip through the EULA.
Now press R to begin a repair installation.

Your system will go through the entire XP install process, but will not attempt to replace any of your existing data. It will simply reinstall the system files and redetect all hardware. Once the process has completed, your computer will reboot and we can move on to the next step.

(re)Activating Windows

As you may know, Windows XP requires an activation code in order to function. This code is obtained from Microsoft in exchange for a numerical hash based on the hardware in your computer when you first activate the operating system. When you make major changes to your computer's hardware, this number will change and your XP installation will deactivate itself, requiring you to obtain a new activation code.

As the motherboard is the central nervous system of your computer, it's about the most major change you can make. Changing the motherboard will almost certainly require you to reactivate windows.

Fortunately, the procedure is simple, though you will need your license key from your XP package. Once the system has booted up and prompts you to reactivate, follow the on-screen prompts to call Microsoft (toll-free) and obtain a new activation code.

Updating drivers and re-patching

The last phase of the operation is to make sure everything is up to date with your operating system and device drivers.

Install the motherboard drivers from the provided CD if necessary. If Windows cannot find the drivers for any devices attached to the new motherboard, you will be prompted for them.

Double check by opening the device manager window (right click 'my computer,' select 'manage' then 'device manager') and making sure that there are no devices with yellow exclamation marks next to them (or at least no new ones). These indicate a device that does not have drivers correctly installed or is not working properly. Install drivers if necessary.

The last step is to run your Windows installation through the Windows update process again, since the repair install will remove any service packs and security patches that you had previously installed. Connect to the Internet and run 'Windows update' from 'start menu\all programs.'

Once the update process is complete, your system should be good to go