I am assuming that it is Windows 8/8.1 if there is no COA.
Agreed, I would clone the system. Your other choice is to have purchased an install disk when you bought it, as recovery disks are fairly useless if you have real issues or the HDD dies.
Your activation key is stored in the bios, and if you want to know what it is open an elevated command prompt window (right click open as admin) and type in this string:
powershell "(Get-WmiObject -query ‘select * from SoftwareLicensingService’).OA3xOriginalProductKey"
Since you have an OEM install, you can reinstall with your key if you can find the DVD image: en_windows_8.1_with_update_x64_dvd_4065090
Unfortunately, MS only provided it on MSDN, unlike the free distribution of Windows 7...