No, you don't need to fdisk/format/fresh install Windows.
Modus's FAQ.....Helping Windows Survive a Motherboard Upgrade
Granted.....I personally have only changed mobos with W9x (even changed from VIA to Intel), and I always had a cloned hard drive in case there were problems (there weren't). I fresh installed W95a in '96 and have upgraded through W2K, with never a fresh install. No way I'm gonna attempt to reinstall all the stuff I've got installed. I couldn't even find the original cds for half of it.
I believe BCYL may have been getting at the following from the FAQ:
Misc. Notes:
- Reportedly, Windows 2000 and XP can be tricked into doing this stuff for you. The procedure is this: Shut down, install your new hardware, power on, and enter your system BIOS. Make sure your First Boot Device is set to CDROM. Insert the Windows 2000/XP setup CD and boot from this disk. (You may have to "press a key to boot from CD" as the prompt says.) Skip the initial prompt asking to repair your existing installation. Then proceed to the screen where you select a partition, and choose your existing Windows partition. Setup will detect your existing installation and ask you to repair. Say yes. When Windows Setup is complete, you should have a fully working installation with all your old user and application profiles. Everything should be intact, except your hardware and driver settings, leaving it fresh for your new motherboard.
- Sysprep, a Microsoft tool for preparing a Windows 2000 system for disk cloning, is useful when changing motherboards. Among other things, Sysprep removes all references to the local machine's hardware devices. You could run Sysprep, install your new hardware, and reboot. However, the procedure is more complicated than the Windows Setup CD repair method described immediately above. Sysprep is best suited to disk image deployment. You can find Sysprep binaries and documentation at
http://www.microsoft.com/windows2000/techinfo/planning/incremental/sysprep11.asp.
--Randy