I did this not too long ago. All you need to do is get rid of the drivers that correspond with hardware that you wont have anymore. For example, a new motherboard usually means a new onboard sound, so uninstall your sound drivers. They can probably be located in the Control Panel -> Programs window. If not there, go into the Hardware Manager and uninstall/disable whatever you need to. Anything thats motherboard specific should go, although there isnt all that much. There is no software that corresponds to processors. Once all that is done, you can swap the hardware and install the new drivers that came with the new motherboard.
Do as the previous post.
Because you are using a new motherboard and cpu vista will see it as a new machine anyway, even if you just change the drivers you will still have to re-activate.
If you are using an OEM version of vista you may have to buy a new licence.