Technical Difficulties

So, for whatever reason my computer isn't letting me upload any pictures, it's saying I need to "reformat" my SD card. I've never had a problem with it before, so I don't know what's going on. If any one has any ideas, please feel free to leave a comment. Also, whenever I was able to upload pictures before, if I took it directly from my camera, which is the easiest, when I went to download the pictures it would say "image unavailable." Any ideas there?? Hopefully I will be able to get this resolved soon. Thanks!