The process cannot access the file because it is being used by another process.

 String[] files = Directory.GetFiles(user_pic_path);

        if (files.Count() > 0)

        {

          FileInfo _info = new FileInfo(files[0]);

          bool found = false;

          foreach (String _file in files)

          {

            _info = new FileInfo(_file);

            if (_info.Name.Equals(_peer_name + _info.Extension))

            {

              found = true;

              _fpath = _info.FullName;

              break;

            }

          }

PeerContents updated_contents = getPeerContents(_peer_name); ;       

        updated_contents.img = null;

        picbox_peer.Image = null;

if (found)

          {

            String files_path = Path.Combine(received_files_path, _info.Name);

            overrideOk = false;

            int i = 0;

            String ext = _info.Extension;

            String nm = _info.Name;

            _info = null;

            while (!overrideOk)

            {

              try

              {

                File.Copy(_fpath,files_path,false);

                overrideOk = true;

              }

              catch (Exception es)

              {

                i++;

                String f_name = nm.Substring(0,nm.Length - ext.Length);

                files_path = Path.Combine(received_files_path, f_name + "(" + i + ")" + ext);

              }

            }                                   

          }

 String fileName = openFileDialog1.FileName;

        FileInfo new_info = new FileInfo(fileName);

        new_path = Path.Combine(user_pic_path,_peer_name + new_info.Extension);

        overrideOk = false;

        while (!overrideOk)

        {

           try

           {

             File.Copy(fileName, new_path, true);

             overrideOk = true;

           }

           catch (Exception es)             

           {

             File.Delete(new_path);

           }

        }