Hi, I'm installing windows 8.1 pro as part of upgrading my computer, and I've never installed a new operating system on a machine that already has data on it. I want to keep as much data as possible, especially steam games. I have two hard drives, a 1TB one that the operating system will be installed on, and a 2 TB one that has most of my big programs on it like games. What gets deleted when you install windows 8.1, and what can I keep. Can I move stuff over to my other hard drive before installing to keep the data? Should I plug in my second hard drive before installing windows? Should I wait until everything is working before plugging in the second hard drive? Also, I might not have internet for a day or two once I upgrade and install windows if that matters. Thanks for the help! P.S. If anyone has any tips or anything about installing windows, it would be greatly appreciated, I'm scared of messing things up.