I purchased an ASUS CM-6870 system that had Windows 8 installed, I wanted to upgrade to Windows 8 pro. After installing the CD and going through the process, I received an error that it could not upgrade. I called the ASUS support line and after a few tries and changes to the bios my system no longer boots up not even to the original windows 8 that was on it. The support line wants me to send the system in so they can take a look and I have to pay my own shipping and it will waste a lot of time. They were no help at all not only did they screw my system up they want me to wait. I bought another system thinking maybe it was the unit that had the problem but I got the same issues with that one.