OEM is OEM its linked to the hardware that it came with.
However its not going to kick up a fuss if you install it elsewhere, and automated activation should still work in theory.
If you call microsoft and want to reactivate it, just "neglect" to tell them that youre moving it, you could simply have upgraded the parts in your computer.
The computerised "enter group A, B, C" nonsense wont know the difference either on the phone. You should be fine.