uses ShellAPI; 

function MrsGetFileType(const strFilename: string): string; 
var 
  FileInfo: TSHFileInfo; 
begin 
  FillChar(FileInfo, SizeOf(FileInfo), #0); 
  SHGetFileInfo(PChar(strFilename), 0, FileInfo, SizeOf(FileInfo), SHGFI_TYPENAME); 
  Result := FileInfo.szTypeName; 
end; 

// Example: 
procedure TForm1.Button1Click(Sender: TObject); 
begin 
  ShowMessage('File type is: ' + MrsGetFileType('c:\autoexec.bat')); 
end;