This is a good program to take the pain out of renaming 10, 100, 1000 or more files. The Bulk Rename Utility is a wonderful tool. The user interface looks complicated but actually you only need to use one or two buttons. The rest are options which I won't even begin to explain to you because I don't use them. You are free to explore them or read about them on the "Tutorial" section of the site (link given above). I saw this utility program over at Hak5 and have been using it ever since.
How to Use in 3 Steps:
1. Write the name in the "Prefix" field of the "Add" section.
2. Choose the files you want to rename.
3. Then press the big "Rename" button.