HI!  
 
Well, after many years of faithful service from my X58 Classified (i7920, muliple gpus-current gtx970) it's time to build a new system (meaning the bug has bit and it itches too much..... since this baby could soldier on a while longer).  Here is what I have ordered so far:
i7 6700K
Z170 Classified K
CORSAIR Dominator Platinum CMD32GX4M4A2666C15
CORSAIR HX1000i psu
CORSAIR H100i V2 cooling
SAMSUNG 950 Pro 512GB ssd PCIe 3.0 x 4, M.2 Gen 3
SAMSUNG  850 Evo 512GB ssd sata III
Windows 7
GPU ?, will probably take my EVGA 970 out of current system and put one of my EVGA 580 in the old one until 1080s drop a bit in price
 
I haven't decided if I'm going to get another case or transplant my current system into one of my older cases.  I kinda want to try a horizontal mb case but I haven't found one I like.
Edit: Decided to go with Fractal Design Define S for the time being

oh dear....sounds like a hurdle...but maybe I can work it out :)
 
Maybe I can install on the 850 evo ssd and do the mirror thing like you said.

This FAQ article may help shed some light with Windows 7 on M.2
http://www.evga.com/support/faq/afmviewfaq.aspx?faqid=59620
 

I decided to get Fractal Design Define S Black Window because it's well reviewed, fits my current "needs" and is on sale for 69.99 shippped no tax!
 
http://www.newegg.com/Product/Product.aspx?Item=N82E16811352055
 

nowcontrol
Did you make a typo? or just not research your cpu/board choices well enough?
 
The will not fit the Z170/LGA1151 board, you'll need an X99/LGA2011-3 board for that processor.
 
An is the current correct cpu for a Z170 board. Also the upcoming Kaby Lake i7 7700K will work in a Z170, too, with a bios update.

So you're saying that the EVGA Z170 Classified K 142-SS-E178-KR is going to support the intel 7700K with a BIOS update?

Okay...so even though I delayed the build a bit for that pathetic EVGA 12 Days of Lame Sales sale, I'm making progress.
 
I could not get windows 7 to install onto the m2 drive no matter what combination I tried from the various posts/faqs/guides/etc......So instead I installed on samsung 850 evo ssd and migrated the os to the m2 samsung using samsung software.
 
Current issues are:
I can't format/erase the 850 evo ssd....I even removed my m2 (next time i'll just disable it so I don't drop that tiny screw... lol) and created a boot "disk" usb drive from samsung software.  The instructions said that was a way to erase the os off the samsung evo ssd and set back to factory settings but I can not get the usb to boot over that ssd.  I can get a rom disc to boot over the ssd, but I can not get thumb drive to boot.  I have oem discs that don't have the format option so i'm kind of at a loss for what to do.  To be clear the 850 functions great and if I wanted to use that as os disc then no problems but I want to get the os off that one since I have it on the m2 now.
 
Second:  I can't get Corsair Link software to install for cpu cooler.  I'm using the latest version from corsair website and even tried re down loading and also tried an earlier version (suggestion by corsair tech).  The installer runs through the whole thing and when I click finish nothing happens and there are no files put on the computer.  Called Corsair tech twice...no help...the second guy said to reinstall windows.  LOL no, just no... it's a fresh brand new and updated install of windows, which you know takes a significant amount of time...instead if I don't get this resolved in a few days I will RMA your product for a refund and get another manufacturers product.
 
 

Oh ...I'll give that a go.  I did set boot for usb first and even tried the boot override and many different combos from bios.....
 
Before I gave up on reading the 850 while operating on the m2 I did plug / unplug the sata cable into the 850 hoping it would appear on the sytem but it never did.  But I gave up on that and tried to just wipe it with a usb procedure from samsung, but now you have given me the idea again...thanks

No luck with that Cool GTX....but I was tired and didn't try every possible setting...just the most obvious ones...maybe I'll take the ssd to my X58 platform and wipe it there

Well, I don't have one of those but I may try one out...another good suggestion thank you.

I'm still unable to use my second ssd.  I took my 850 evo ssd to my other computer and used quick format on it and now I want to use it as a second drive in my new pc:
 
Main SSD is m.2 Samsung running Windows 7 just fine.
Secondary SSD 850 evo (blocks m.2 drive from being detected and steals boot sequence, which fails because it's an empty disk)
 
So when I have 850 evo plugged into sata port and try to boot computer it won't boot because it's effectively and empty disk that is taking priority over my windows 7 boot disk operating system drive which is the m.2 drive. 
 
In the bios there is no differentiation between hdd and ssd not to mention different versions of ssd.  I have boot priority set to hard drive but the empty 850 evo on sata blocks the m.2 operating system drive from booting.
 
Any suggestions?  Was I clear on my dilemma and does anyone else run m.2 operating system with secondary ssd, windows 7, on evga z170 board successfully?
 
Thank you

it sounds like the MBR is still on the 850.
try using minitool partition wizard on your older system with the 850 plugged into it and have that wipe it clean.
and +1 to the disabled sata ports while using M2, tho you did say it is trying to boot from it so I doubt that is your issue.