Right-click Start then select Explorer
Select the menu Tools - Folder Options dialog box will appear as below
Select the View tab and uncheck the option Hide extentions for known file types (which is circled in red) then all extensions will be displayed. Then you can change the extension in a way rename the file.
For example, change the file berextension. Rar into berextension. Avi
After that his next movie will file extension its plasticity, such as the original title of the file to be High School Musical High School Musical.rar. Ago. Rar behind the name change to the file. Avi or or other extensions as necessary.For example, change the file berextension. Rar into berextension. Avi
Note:
This method is not used to change the type of file. This method is used to change the extension back which has been modified by the manufacturer. If you want to change the file type then use as desired softwere Converter. (^ _ ^)