Solid Renamer is a powerful tool which can help you rename an entire folder of files in a single operation.
The process starts by thinking about the rules you're going to apply. There are five options. "Trim" removes text from a given position in the current file name; "Insert Text" adds it; "Enumerate" allows you to add numbers to your files; "Replace" will replace your defined text (regular expressions are supported) with something else, and "Change Case" can change the case of each name in various ways.
Each of these options is more configurable than you might expect. If you're adding numbers to a file name, for instance, you can define the starting number, how many leading zeros you need, the character position (in the file name) where you'd like the number to appear, and whether that position is starting from the beginning, or the end of the file name.
What's more, you can then combine as many of these rules as you like, perhaps creating something that will trim the beginning of your names, add a number to the end, insert some other text somewhere in the middle and convert everything to lower case (or whatever).
If you think this can get complicated, then you're right. And that's a potential problem, because renaming thousands of files incorrectly really isn't something you want to do.
Fortunately the authors understand this, though. So once you've dragged and dropped your chosen folder onto the File List, clicking "Preview" will show you precisely what effect your rules will have on each file name. Once you've scrolled down and made sure everything is fine, clicking Rename then carries out the operation for real (and in just a few seconds).
You still have to be careful, of course. You're not forced to use the Preview function, and if you accidentally rename some critical executable files then you could run into serious trouble. But as long as you're cautious, Solid Renamer should prove a capable tool which can easily handle all your batch file renaming needs.