I've been using my Raspberry Pi model B for a few weeks now with a total of three different SD cards so far. All of a sudden, one of these SD cards, which is 8Gb can no longer be booted from, although the other two (both 4Gb) still work. I think something on this card has been corrupted, although I can still see various files on it when I insert it into my laptop. On this card, I used NOOBS to install Raspban, OpenElec, and Raspbmc. I've installed lots of video add ons under OpenElec, so I don't want to have to install them all again. What's a quick and easy way to make this card bootable again?