Yes, you can do what you're talking about. You can only have it installed on one desktop and one laptop at any given time.
Creating an image and you keep wiping and redoing would keep you in the agreement.
I haven't tested with the Retail version - I only have the OEM and VLK versions but I do know that after an image of an OEM and combining Sysprep, you have to call to reactivate only because its OEM.
If you do not use Sysprep and take a true unchanged image, you shouldn't need to call or reactivate.
You also have to make sure your motherboard is the same chipset, otherwise the image will most likely fail at the HAL level.