NAS and a Gaming Rig

[Xtremeacecow]

*SPOILER ALERT FIRST LINE

On Vessel, Linus posted a video about a gaming rig and NAS combined with UNRAID from Limetech. It was similar to the 2 gamers 1 CPU video. 

I have a gaming rig already built http://ca.pcpartpicker.com/p/h8RnP6 and my NAS (WD MyBook Live), which is non-upgradeable. For power, my graphics card is not overclocked and my CPU is overclocked to 1.25V and 4.5 GHz. I wanted to maybe run a new NAS from my gaming rig instead. I do not necessarily have to use UNRAID, I just want to use my computer as a NAS as well. My mechanical Seagate drive is old, so I definitely either want to replace it or have a redundant drive for that. My SSD currently is my primary drive and  my mechanical one is where I put most of my applications. The reason I cannot just follow Linus' instructions is because I have already installed Windows 10 64-bit Pro on my SSD and I do not want to erase my OS from the SSD or my programs and other files from my mechanical. What kind of setup should I use?