Micro sdhc 4 GB can't working

I bought a sdhc 4 GB memory card yesterday. But the problem is that the files copied into that can’t working in mobiles and computer too… I tried using different computers and mobiles. But not solved. I tried after formatting. No result . What can I do??? Pleas help me… Some folders contain files and working.  Some have files and not working. Some seems to be empty but  have file size.  Some have both working and non working file… I am on confusion

It would help if you tell a bit about the files and what you are trying to do.