Shankar wrote
I need an Files Extension Changer, where I can download it?

T S Ganesh of BR Hills suggested:
You could try the 355 KB Extension Changer, a freeware, at http://www.seegh.com/extchanger/index.php?view=download. Using Extension Changer can help change hundreds of files extension in one go. No need to uncheck 'Hide file extensions of known file types' option from the 'Folder Options' dialog or renaming the file from DOS.
     NSS