I installed the Windows Technical Preview Evaluation Copy Build 9841 (which will someday be Windows 10) on my PC which overwrote my Windows 7 operating system, Now Ghost 15 is requiring me to enter the product key. However it won't accept the product key that came with Ghost 15, and which was successfuly when I installed installed Ghost 15 on this computer. It indicates that it is not a valid key. I only have 29 days left before Ghost becomes inactive. Norton Ghost 15 works for this Windows version as I was able to create a backup.