Can't copy any files to my external hard disk

Please help me. I brought a Hardisc and I copied some files on my laptop to hardisc. After that I can't copy any files to my hardisc. When i try to copy, nothing happens. I can copy files from hardisc to laptop. After that I formatted the hardisc and now also facing the same problem. Please help me with that. I think it is because of some virus problem. I was about to format my system after coping the files. Please suggest me a way to solve this problem and to use my hardisc normal.