OEM, the EULA saya you can only install it on one machine, when that machine dies so does that copy of Windows.

 

Standard- Retail  The Eula say you can put it on one machine, but when that machine dies, you can put it on another, and when that machne dies, you can put it on another.  Best option if you build your own PC's

There is a bit of give in OEM as well. You may upgrade components (such as video card, RAM or sound card) and still be able to activate the same OEM. When the system is drastically changed (say a new MB, RAM, HD etc..) then you won't be able to use that OEM.

 

Fine line if you ask me, and I'm sure there are ways to wiggle your way through almost a new system and be able to still use the same OEM (after making that phone call to MSFT that is).

OEM software is forever bound to the machine it came with....no wiggle room there.