retail and OEM/OEi are the same, retail has a box and has the same license as OEI, OEM is the same but its not transferable to a new user (so u cant sell it), u will probly want biz x64 OEI. i have never had to call MS for vista ive installed it about 15 times and changed from x86 to x64 then from a 939 single core to a core2 and i had no problems


also never buy an upgrade they are dirty installs and dont let u change hardware