I have a windows 8.1 desktop PC. I plan to install a 250 GB SSD. This particular PC was running windows 7 and I upgraded to windows 8. I have misplaced my licence key. How do I install the new SSD? Keep in mind I have misplaced both licence keys from Windows 7 and Windows 8 and I do not want to pay for that OS software the second time. Thanks in advance for your help.