It's really hard to suggest something about your situation because you are in dual boot. If it's just Win 8 in your system, you could just go ahead and hit repair without worrying about the other OS installed in your hard drive. I guess this just proved my point that doing a dual boot on a single hard drive with the main OS can really be a big headache. I wish you luck and I hope someone who commented here before who had years of experience with dual boot on a single hard drive will come back and help you out because I don't dual boot on a single drive.
Cheers!
I have done this before in a dual-boot scenario. I lost the ability to boot into Windows 7, but I regained it after I manually added it to the boot path using msconfig, double checking all boot paths before rebooting
