> Nu mano ziniom Windowsu raktai priklausomai nuo bitu skyresi tik pas XP, 
> bent Win7 atveju ne karta yra po RAM upgreido i kompus vietoj 32 
> instaliuota 64 bitu OS, panaudojant originalu 32 bit rakta.

MSO2013 PKC (retail) leidzia persimest, o MSO2010 ne.

http://download.microsoft.com/Documents/UseTerms/Windows_7%20Home%20Premium_English_95d28e40-a649-40d7-abff-bdd912a80dc0.pdf

d. Alternative Versions. The software may include more than one version, 
such as 32-bit and 64-bit.
You may use only one version at one time. If the manufacturer or installer 
provides you with a
one-time selection between language versions, you may use only the one 
language version you
select.

pazodziui skaitant yra "may", o ten kur "only" - jis skirtas "only one 
version at one time".

http://www.microsoft.com/en-us/Useterms/OEM/Windows/10/UseTerms_OEM_Windows_10_English.htm

d.      Multi use scenarios.

(i)      Multiple versions. If when acquiring the software you were provided 
with multiple versions (such as 32-bit and 64-bit versions), you may install 
and activate only one of those versions at a time.

O cia kaip? jei gavai 32bit netyciom ir nera 64bit (Win10 32bit OEM'e), tai 
galima naudoti tik 32bit?