I have a Acer desktop with two hard drives and I would hope it is as easy as just buying a Windows 7 disc and choosing the hard drive I install to, but I have been told that things like GPT or UEFI on my current hard drive, or installing raid when I do the install could all cause problems between Windows 7, and Wndows 8.1. 
So my issue is how do I look at my own system to find out if any of these problems / conflicts will occur? I don't really have much of a clue about conflicts between operating systems. My second hard drive comes up as a data drive under my computer, but it doesn't have any data on it.

So my issue is how do I look at my own system to find out if any of these problems / conflicts will occur? I don't really have much of a clue about conflicts between operating systems. My second hard drive comes up as a data drive under my computer, but it doesn't have any data on it.