SD Card Mystery

[Juslisten]

Hello I have a very perplexing situation on my hand. I have a 4GB SD card by transcend. Recently, don't ask me what happened but everything disappered (music, pics, programs) besides a few items (some cabs I had saved, my microsoft documents). The ironic thing is that with all of these items gone my memory on my SD card did not return. When I tried to re-install some programs I would get a prompt saying that it would overwrite the current program. Remember nothing was showing up. I tried this with my music but I didn't get the same prompt. I just want my memory back. I am lost and I have no idea of what to do. Please help me with any thoughts and ideas you may have. Thank you.