Get Windows from original sources. The 75% CPU usage could have been caused by faulty driver. The key works if it's legit, because it's signed to your HW_ID.
Linux distributions have been added with malware and spyware aswell, because people don't check if it's a legit download or not.
Check if it's original source, the sites provide hash-key. Everything else can be injected with malware. Even with same size. This was the thing with people thinking they're downloading legit updates for their mobile phones and even the software can't detect if it's correct or not.