Please don't say I didn't warn you. If you reserved your upgrade of Windows 10, it is likely high time that you backup your system, right away. Most commercial backup software will work well with Windows 8.1 at this time, including the front-runners Acronis True Image 2015 and Paragon. These are not endorsements, just the facts. It is not advisable to perform the upgrade without backing up your entire hard disk to a restoration image that can be recovered on boot-up in the event of a disaster. Even the built-in backup feature in Windows 8.1 and Windows 7 may be advisable as opposed to nothing. To let you know, I have personally begun to back up systems in the event that this upgrade seriously wreaks havoc. I cannot say that it will, but let's be safe, rather than sorry. Do you agree? Best regards and good luck.