Yes, disconnect any drives other than the one you are installing Windows on to avoid issues. Just unplug it, it's as simple as that and replug it in after Windows is installed when computer is not powered on. Switching to Z97 won't have any effect on Windows as long as you're doing a full reinstall of Windows, all the drivers from your previous Windows will be gone, and you'll be able to install the new drivers that came with the motherboard, (or better yet, download the newest versions from ASUS website). Windows will likely only take 20GB or less for the install, so you should be completely OK on driver installs space-wise and if for the space that Windows uses for other things. Chipset drivers should be first installed, then do the other drivers/utilities. Leave the BIOS at optimized defaults for now, make sure it boots up, and then you can go back and change the memory to use the XMP settings. First boot will normally take you to BIOS first, and once it's there, you can restart and go into Windows. Hope this answers everything for you.