I plan on building a new system myself so I would need to buy a copy of Windows 7. I will probably go with the Professional version as this allows me to run some programs in XP mode which might come in handy. Does it also allow me to run programs in the 32 bit mode if I buy the 64 bit version? I was thinking of buying the OEM version of that as it is the cheapest. However, a page on this site claims that this version "is forever locked and bounded to the computer (motherboard) of which it’s installed." What happens if one's motherboard goes bad? Would one have to then buy a new copy?