I just built a news system and did a clean install of retail 8.1 Pro 64-bit. Activated it without problems and did a clone to file using Paragon. Copied the clone to multiple drives to use on the same computer, to keep gaming etc on separate disks. Everything worked perfectly until this morning when windows says its not activated and key is in use on another computer. The key has been used, but I swapped out the motherboard, cpu and ram and did a fresh install. The phone activation worked without a hitch, but now activation has failed. Its only been running a few days, but I've been able to swap drives without a hitch. Is it the fact that I use multiple disks on the same computer or is it the fact that I have previously used this key on different hardware? The key is not installed on any other computer. I ran this system of swapping drives with Windows 7 Ultimate without problems, but maybe Win8 is different.