Just for reference sake , i asked Microsoft the following in an email:
"Could I buy a Xbox for Windows and use the kinect on my Xbox on occasions? Or is the only option to buy 2 different Kinects?"
As we understand, you want to verify if you can buy Xbox for Windows.
We regret to inform you that there's no available Xbox 360 for Windows only Kinect for Windows. Also, the only option is to buy two different Kinects.
There you have it.