The Windows product key is tied to several hardware components. The most important of these components is actually the MAC ID of the network adapter used to connect to the Internet. As long as you have not changed this device there is little chance you will have problems activating your license.
If you do have issues getting it activated, call the phone number you are directed to during the activation process. It is a simple process of activating Windows via the manual phone method. Either way, not an issue.
For the Blue Screen problem it is most likely caused by a driver. If it happens again download BlueScreenView and when you run it, the application will scan your crash files and list the most likely culprit in pink. If it is a graphics related file, update your video card drivers. If it is a network related driver, update your network drivers, etc.