Dear All,

My Macbook Air installed Mac OS X 10.9.4 and Win 7 Ultimate. I install rEFIt to use boot menu. I have problem that the rEFIt automatically add one more "Boot legacy OS from HD" on boot menu. Please let me know is there any way to remove this boot legacy on boot menu?
I had read this thread: but can not use the code: 'sudo dd if=/dev/zero of=/dev/disk0 bs=440 count=1'
Mac terminal show that: dd: /dev/disk0: Resource busy
My mac have no Linux. How can i use this code on mac?

Thank you very much!