I have read a few reviews about Windows 7 and It seem to be that if one buys the OEM version of the any version of Windows 7 and if they want to upgrade the licened computer of that software it voids the software. Is this true?
Your copy of Windows is locked to the PC on which you purchased it. You cannot transfer that license to another PC.
You can upgrade any components or peripherals on your PC and keep your license intact. You can replace the motherboard with an identical model or an equivalent model from the OEM if it fails. However, if you personally replace or upgrade the motherboard, your OEM Windows license is null and void.