Au cas ou tu ai la flemme de lire :
With any Windows 7 license, you can reinstall either 32bit or 64bit of the same version.
You can always reinstall Windows 7 as many times as you please. It should not even require the robocall to MS if it is on the same hardware signature.
Any retail copy of Windows 7 except OEM can migrate to the machine of your choice, requiring an activation robocall to MS to reset the hardware signature.
There are multiple reliable reports that MS is allowing exceptions for mobo and even computer change with Builder's OEM however this can not be relied upon as it is case-by-case basis.