Q: OS X Yosemite v10.10.2, Boot Camp 5.1.4. I have message "Boot Camp only supports Windows 8 ..." but I have Windows 7. How can I solve this problem?

You can only run 64-bit OSes on this MBA. Are you using 64-bit media?

BC Assistant is a utility that partitions your disk and creates a bootable device to boot from. For Macs after Late 2013 models, Windows can be installed without using BC Assistant. It requires the creation of a manual partition of Free Space or FAT format and booting from a bootable Windows device. If you have Windows Installer on physical media on USB, it is easier, otherwise you can use a tool like Rufus USB (https://rufus.akeo.ie/) or https://technet.microsoft.com/en-us/library/jj200124.aspx?f=255&MSPPError=-21472 17396 and boot from it and select the Windows-designated partition. Windows will be installed using generic drivers. You can download Windows support software appropriate for you hardware from System requirements to install Windows on your Mac via Boot Camp - Apple Support, some of which is only available via BCA's Download Software option.

If you run into any driver issues, WHQL drivers can also be used, but should be tested first.

You can install W7 64-bit without using BC Assistant. Please see the previous post.