Today I need to rename a batch of file about >100 file from .jpg to .png for the testing of application purposes. Google around and found this free solution which make my life easy.
Select the folder where the file where the extension to be change and press Shirt and Right-click on the folder, and than select Open Command Window Here
You will now see a Command Window with the current folderdirectory open. Now type the following command line,
ren *.(current extension name) *.(extension you want)
Since I want to change the extension from .jpg to .jpg, in my case the command line would be,
ren *.jpg *.jpg
Now all the files inside the folder will change to the extension you want. It’s that simple.