djsioni :
i bought the i7 7700k is it only exclusively for windows 10
I'm using the i7-7700k with an ASRock Taichi mobo. Yes, the new Z270 Mobos do not have USB2 ports, and Win7 doesn't have native support for USB3.0.
There are a few options. With the ASRock Taichi, all you have to do is turn on legacy USB support prior to installing Win7. This is what I did: I swapped out my old ASUS 775 chipset mobo with a Taichi loaded with 32GB of RAM and an Intel i7-7700K chip. Turned the box on and Windows 7 64-bit started up perfectly, but my mouse and keyboard were dead. I restarted, changed the settings in the Bios for legacy USB support, and then when Windows finished loading my keyboard and mouse worked just fine. I then installed the necessary USB3.0 drivers, restarted the computer, turned legacy USB support off in the Bios and everything is fine.
Another option is to create an ISO image of your Windows installation with USB drivers.