Nereus
 
Broke down the build, and in the process of putting the cover on the CPU socket, I bent a bunch of pins. *sigh*.  Paying to send the motherboard in, get socket repaired or replaced, send back, then sell it.. lucky if I break even, so I tossed it in the trash. Yeah you heard me, I just tossed out a near brand new Z170 Stinger.
 
At least a couple of the parts I salvaged and rebuilt my wife's rig - like a brand new EVGA Supernova P2 850W PSU. Upgraded her to a Z97 Stinger too. I have a big box full of parts to sell in the near future.. including an i7-6700k and some DDR4 ram, if I can't return it.
 
It's currently 4:30am and I am finally sitting down and having a well-deserved ice-cold beer (Corona), then going to bed.. until my daughter wakes me up at 7:30am, lol.
 

I was honestly hoping you'd have better luck with your build than the others. Sorry to hear about the bent pins in the CPU socket. The same thing happened to my P67 motherboard so it still sits in its box hoping that someday someone with a steadier hand can come along and straighten the pins. Your bad luck sounds just like the story of my life. Don't give up. Since it can't get any worse, it can only get better. Good luck to you. Keep on plugging, Nereus! 
 
P.S. "Never give up, never give in.", Dr. Who.

Man, Sorry to hear to problems you are facing. That really is a bummer. But in all honesty I would think that the Z170 boards do support windows 7 since some people will have to upgrade to 10 from it. Also there have not been a lot of complaints here or anyplace else on the forums about other manufactures. Either it can be a driver problem or maybe something is wrong with the motherboard. That is what i can think. 
 
If EVGA didn't fully support Windows 7 i believe they would have said something. Personally i'm going with ASRock Gaming ITX but everything else will be EVGA because of there amazing customer service.
 
Honestly i wish a Tech would come in here or maybe you should start another thread to get the Tech attention to maybe see what could have been the problem to help others.
 
Thank You hope you have better luck man. Trust me i was in the same position 4 years ago when i have a computer break every 5 months because of bad luck with parts
 
Joe

I too gave up on installing Win7 pro to upgrade it to Win10 pro, I spent 4 days installing and getting to the point of final install to get the blue screen stating there might be a hardware change or software change then proceeds with a countdown and then dump so fast its hard to read then reboots with an error window that comes up and says can not proceed and then says to reinstall Win7 again , tried installing on a Samsung 840 ssd drive and a regular WD drive no luck at all. end up using my win8.1 Home with no issues. I had no idea at first Win7 had this issue on this board leaving me with a Win7 pro OS sitting in the desk drawer. Oh And I did the cmos reset, one drive set up, one memory stick in slot 2, and shut off anything not needed in the Bios, slip-streamed the win7 install CD, all taking up a lots of wasted time with no success. Anyways it does say mother board will support Win10 Win8 and WIN7. I do know that there doesn't seem to be to much discussion on this problem other then a few others in my predicament with no real support on Win7 installing issue .After hours on the phone with Microsoft they tell me to contact the board manufacture the issue is with the board which boots perfectly fine on Win8.1, what a run around. Just a little frustrating.  Fixed in new 1.05 bois update
Louy1

The only hardware I did not remove are my evga gtx770 video cards when trying to install win7 and I mentioned in another post my Bios has an issue with the software reset it locks up I have to use the cmos reset on the mother board to reboot.. Other than that all ran perfect with no issues on my z87 board.
Louy1

Nereus
 
Thanks all. I did get into the o/s, but could not get USB3.0 drivers to load, and the USB2 ports were not working as they should. The board is gone now - never really had any issues like this for years, so I guess I can count myself lucky.. doesn't pay to be an early adapter I guess. Or maybe just a bad few days for me, because I rebuilt my wife's rig with a Z97 Stinger and now am having issues with the audio drivers on that, and then just started getting a disk error now so BAH!!!!   LOL.. had started tearing down my X79 Dark, so put it back together again just now also and everything installed fine not a problem anywhere. Yay. I think that deserves a cold beer.
 

On your Z97 motherboard look in the device manaager and under audio devices uninstall the NVIDIA HD audio (there might be two entries). Once done see if audio is working.