Right the file you wish to rename. In the menu that opens, click 'Rename'. Type the new file name and press 'Enter' key.

Also, make sure you don't change the file extension (after the . ) when you do this.

It's easy to accidentally do it but you'll get a pop-up warning if you mess with it.

(.jpg should remain .jpg, .txt should remain .txt, etc.) 

Select the file which you renaming 'N' press Right Click of Mouse and select RENAME option in pop up menu. Now write new name of file. this is the method to Rename a file........... O.K.