BrokeAgain

I have found where I can buy one on ebay. Can anyone tell me how to back it up in case it happens again?

After finding and looking at this site for a while and not finding what I need I figured I would just ask.  I have a avic 7200nex and got the loading screen issue..no load, no screen control no button control but backup cam still works.  I am guessing its the internal sd  card issue...I took it out, and put it in my pc....ACCESS DENIED...Do I need an app to see whats on here or is that an indication the card is bad?  I have read about extracting the file and everything but cant seem to find  the file anywhere..ANy help would be greatly appreciated...I really dont want to shell out the money for a new headunit right now