Reinstall Windows 7 on a Non-Dell motherboard?

Im looking into buying a new motherboard, of course i'd rather not have to buy another copy of Windows 7 so im asking if its possible(and legal) to use the windows 7 product key that came with my Dell Inspiron 570 to install it onto a new motherboard. Im assuming its not but i might as well find out for sure before i spend 100 dollars on a OS i may not even need.