Do you mean that you were sent a product key for 2.0 testing and it was sent to your subscription LiveID? You can use that key to activate with *any* LiveID, so go ahead and use a different LiveID to activate your beta installs of OneCare 2.0.
If you already activated under a different LiveID with the key, you can't change the LiveID for your beta subscription, so you'd need to uninstall and reinstall, but you will not be able to activate with that used key again.
You *can* have a beta and production subscription with the same LiveID, although it isn't recommended as it could cause confusion at some point in time. So, if you have activated with the same LiveID for 2.0 beta and a product key that is associated with a real subscription, no problems. Just go ahead and install additional 2.0 PCs as desired and activate with the same LiveID. Since the 2.0 beta communicates with a test back end environment there will be no impact to your production subscription. At the end of the beta, all 2.0 beta machines will likely need to be reinstalled and activated once again with a production subscription LiveID.
-steve
