REN

Changes the name of the file or files you specify.

Note:
You can use the command in two ways:
1. Without wildcards:

REN file1 file2

2. With wildcards:

REN *.ex_ *.exe

If you are using Windows 9x/Me/NT/2000, then in an MS-DOS prompt window, you 
can use REN command to change the name of a directory.

For more information, please refer to MS-DOS Help or Windows NT 
command line command help.