Ive only been running the new motherboard for a few days, but I seem to have gotten really lucky. After upgrading the motherboard/CPU it rebooted into vista and got some "cant find drivers for hardware" messages. I installed the drivers from the new motherboard cd and rebooted. It found the new hardware drivers and has been working.
Thats the first time I have been able to do that. I dont know if Vista is more friendly than XP was, if I was just plain lucky, or if I will sometime in the future find out something isnt working right and have to reinstall.
If staying within the "same family", meaning you had an Intel chipset and so does your new board, you shouldn't have to do anything. Its always a good idea to delete old drivers before you shut down. Lan, sound, etc. Don't delete the video drivers if you are moving the card over to the new mobo.
If you get stuck, the repair install will work. You do this by installing a new copy. It should then find the old build and offer to repair it for you. Don't hit R when its done loading. That takes you to the recovery console, and you don't want that.