vixl2ds :
Well, I have just the key, so it's OEM.
THen technically it can not be -- but that said it doesn't hurt to try and call MS during the phone activation process one of two things will happen --
1.) it will activate fine and the computer system will give you a valid response code to type in (happens sometimes if the old key has not been reactivated too often or in a long time )
2.) it will fail activation and you will be connected to an activation rep that will ask a few question : like is the license being used on more than one system. Depending on your answers and their mood they will either reactivate it for you or tell you that you need to purchase a new license
In either case there is a chance they will activate it for you so is worth a try and even if they do not you can use the system for 30 days without activating so have plenty of time to then order a new license if getting it reactivated fails so nothing to lose in trying !