You can do this pretty much risk-free: 1: Download and install Macrium Reflect free edition. Include the WindowsPE components offered. 2: Use Reflect to create a system image of your entire HDD; store that on separate external media. Also, use Reflect to create a WinPE boot disc. 3: Download and install Win10. You can still do this for free - google it. 4: Use and decide. 5: If necessary revert to your system image by booting from the WinPE Boot Disc and using it to restore your image back to your HDD. It's what I did - except for step 5 which I have never felt the need to do.