It would help if you gave us an idea of the files that were mislabeledd. For example, if you want to relabel a bunch of files from JPG to jpg, one would use a for loop.
If the files are all over the place, you might have to use find and xargs.
Please be a bit more specific, then I think someone can help.
Meanwhile, I'm renaming the thread to be a bit more specific, so that the scripting experts will be more likely to notice it.