A "Mgf's OEM" and "MS OEM" would be the same thing. Now OEM copies of
Windows are bound to the hardware they are sold with. But if you need to
replace a hard drive thats no problem.
Not necessarily. The MS OEM is what "Mom and Pop" builders buy from
MS, usually a disc and license per PC. These are the OEM discs you see
for sale often.
The Mfgs OEM is an OS customised to the particular PC it is sold with.
It usually comes as a restore disc set, or hopefully not in your case,
as a hidden restore partition.