Sam... OEM is only supposed to be installed on the original computer it came with. It's not supposed to be installed on a replacement machine (i.e. the old one is trashed/sold w/o it).

For example, for Win XP, OEM versions are tied down
to the first motherboard/PC that they are installed on and Office works the same as I know it.

The install Office twice scenario is one where you have it on a home PC and can also install it on a laptop, not to be used concurrently.

If the OEM was installed/purchased on a laptop to begin with, I am not sure that applies. But, I do not know for sure.