Windows may boot with the new board out of the box, but it is possible that you will have to massage it go get it to work. If it does work, you should still update all your drivers from the motherboard's web site. If it doesn't the easiest way to do it is re-install and pick "upgrade": This will keep all your programs intact, but replace the hardware drivers and any other faulty registry settings. Even after the upgrade, update your drivers.
If you try to upgrade to your same OS, but are not given the option (grayed out), it is likely because your original disk is older than your current service pack level. In that case, you will need to slip-stream your original OS disk to add your service pack level or newer. You can search how to slip-stream here as it comes up often.