I have the same problem with my new I7. Built from scratch because already had Hard drives and then find I may need Windows clean install. I think best bet is to buy Windows and another hard drive to install so I don't lose info on the old one.
put in fresh Hard drive and reinstall windows (just make sure you are not using the old hdd in a different system with same windows key in use as that's illegal)
After installation you will need to call windows to get the key reactivated for the new motherboard then you can transfer files from the old HDD
If you don't need anything from old HDD, just wipe and start from fresh and do above reactivation code as it is matched up to the motherboard