Hello Romaq, if you have One Care installed on multiple PCs go to the hub PC, open One Care>Manage Your One Care Circle, select the old PC then select "Remove this PC". On the new PC install the One Care trial -
http://onecare.live.com/standard/en-us/3/default.htm To activate open One Care, select "Subscribe" and when asked for a Live ID enter the Live ID and password used to purchase One Care. Your subscription status will be recognized and One Care will activate.