[WIN7] Rebuilding a W7 box

I have a W7 box that I built in ’10 and would like to update the motherboard and cpu. If I did a straight swap will Windows (OEM) and Ofice Pro 2010 still authenticate? Or could I get another W7 disk and just use that code, what about Office? The long way around is to replace the HD, install a new (disk) W7 and use LapLink to move over the files. If I did this will my registry tweeks still be there?? I really don’t want to buy Windows again because of a tight budget. I’m operating on a shoestring as it is.