If you want to batch rename images in the same folder then download IrfanView which is a free tool which you can use to batch rename or batch resize images (amongst many other things).

Once you download the program open it, click File -> Batch Conversion\Rename. Navigate to the folder which contains your images, select them, and drag and drop them to the left white pane named Input Files. Select your output directory, then select the Batch rename radio button, click the Set rename options button and change some of the options if you have to. Click OK and click the Start button and you are done!