Try the DOS prompt (copy c:\yourdir\yourfile.ext c:\elsewhere\yourfile.ext)
alternatively, if it's a file that you know contains ascii chars (i.e. a config file) then open it in notepad, it doesn't care whether the file is in use or not.
alternatively, if it's a file that you know contains ascii chars (i.e. a config file) then open it in notepad, it doesn't care whether the file is in use or not.