How to deactivate a Trados Studio 2015 Licence (only one)

Ho have a licence of SDL Trados Studio 2015 Plus at the moment. Therefore I installed it on two PC. These are critical workstation for my jobs. Now one PC has crashed and I can't free that licence to install it on a new PC. How I can proceed? !!!IT IS EXTREMELY IMPORTANT TO FREE ONLY ONE LICENCE OF THE TWO AVAILABLE BECAUSE THE OTHER IS A CRITICAL RESOURCE FOR MY JOB!!!