I am using a mid-2009 macbook and currently running yosemite. before I am using rEFIt to install win7. now rEFIt and rEFIND is not working and I tried installing win7 after partitioning the drive. but then when I am about to install win7 I am getting the error "non system-disc press any key to reboot" I would have loved to use my win7 DVD but since my mac's DVD drive is broken I have no choice but to use bootable thumb drive. thank you very much in advance