Considering the option to do a fresh install of Win10 on my SP3 Pro. Downloaded the media onto a USB Stick. However reading up on this it seems I may need the Win 8.1 product key (i.e. serial) for my current install. No sticker on the SP3. Do I need this and where do I find it? Somebody also mentioned a driver pack to download and install before allowing Win10 to get online. Any link to that? I am using System Image Backup in Window 8.1 which I believe creates a true snapshot. Does this work and allow me to revert back to 8.1 keeping all my files/setting the way they were when the image was created? I found my bitlocker key and printed it...since apparently that is needed.