Instruct end user to replace broken parts (if any) and reinstall all required software including protected application on original computer.
Protected application will generate new and different Site/MID codes. Once you receive new codes from end user you can decode new MID code, review and compare locking parameters with their previous values. At this point you can decide if you are going to issue free replacement activation code for customer.
NOTE: Activation center (ACEN) includes flexible license reactivation feature where customer can easily reactivate license without valid license removal code in case of disk format or similar computer failure.