I find bulkrename (free from http://www.bulkrenameutility.co.uk/Main_Intro.php) quite powerful. However you didn't tell your exact requirements, except for what you don't want to happen, so I'll leave it to you to study what it can do (be sure you know the basis of regular expressions) and see if it's what you need.
If not, why not your own rename script in vbscript (using the filesystem object) or in Powershell?
One of the great, albeit lesser known, tricks of renaming in Windows is that you can select all files in a directory and then rename one file and it will rename all files in the directory with whatever you chose and then it adds a (2) or (3) and so on at the end of every subsequent file.
Unfortunately, I'm dealing with a case where the () are not only undesireable, but they break the web script I'm using. In order to get this random assortment of images to be in an ordered and coherent list, I'm looking for a tool that allows for bulk renaming with as little complication as possible. I've tried a couple free tools, but nothing has worked for me so far.
Does anyone know of a good tool for this? More interestingly, is there a way to tell Windows not to add the parenthesis? (I'm thinking it might be possible with a registry hack?)