Script:JScript
fs=new ActiveXObject("Scripting.FileSystemObject");
fn=WScript.Env('Focused');
WScript.Exec('Input:"名前の変更","%current%","'+fs.GetFileName(fn)+'","%FocusedName%"',1);
WScript.Exec('SW:0:%ComSpec% /c ren "%Focused%" "%InputData%."'+fs.GetExtensionName(fn),1);

こうかな