So I have put up a post already about having an LCD problem. My imac's screen is completely bright white but the imac works fine with an external monitor. The apple store can't figure out the problem so I'm stuck with using an external monitor or selling it for parts and buying a new computer. For right now I'm going to get an external monitor because it's cheaper for me. Here is my issue, when doing any kind of diagnostic or having to reinstall the OS, I can't see any of this stuff because the external monitor doesn't work in mirror mode until the computer has fully booted up. What can I do about this? Or am I stuck basically?