Considering this build

[SoulEpsilon]

I'm not sure, not to firmiliar with oem just know it makes it so you can't change your build.. maybe somebody else can elaborate more for us and explain it better but if you plan on upgrading in the near future, or future I wouldn't go with oem unless you really had too.

 

[Sukutani]

After a delve into the official win 7 forums, and a brush with an uncomfortable amount of MS glad handing and legal-ese. I have an anwser, OEM versions lock to the motherboard, You can change everything else and retain the license, but if you change the motherboard a new license has to be obtained.

Overall, I'm fine with this. I don't build new pc's very often and I have no intention of replacing the motherboard for probably 2+ years (Unless it burns up or some other awful event).

And the rules may be loose, I remember my OEM XP disc and key were used on 4 or 5 separate builds