So far as your curernt OS is concerned, you should be ok if its not on OEM version. However, it will not validate automatically and you will have to telephone to get this completed. This sometimes also works with OEM versions and I have heard it told that, if that fails first time, ringing at a differnt time might find a moer tolerant person.
You should always reinstall the OS after sucha major upgrade. Each mobo is different and requires differnt drivers from the OS and this is sorted out during the installation process. Failing to do this will result in the OS installing fresh drivers but leaving the old ones in place resulting in a more sluggish and bloated system and possibly some damaged drivers.