I went from a Tyan to an Epox board using the same chipset just a few days ago. I did make a backup just before booting any OS, just in case. 🙂
After the mobo swap, I first booted my throw-away WinME install. I was kinda surprised that it redetected everything (as if it were new) down to the BIOS and memory controllers. Win2K nor XP would successfully boot. FreeBSD 5 and Linux wouldn't boot either.
A few moments later, it occurred to me that the original installs used ACPI. After activated ACPI, everything in 2K and XP were fine. I did have to reinstall drivers for the cards in my system. So, if anything, I would remove all drivers for any PCI cards and external components and reinstall them after the swap. Chances are that the OS will treat them as new devices anyway.
I still can't get FreeBSD and Linux up, even with ACPI. I didn't even bother booting WinME either. I just ghosted a just-after-the-first-install-reboot WinME image and will wait for my new video card before I try it.
-SUO