MicrostockGroup

Total Commander can do this:

http://www.ghisler.com/

Adobe Bridge -> Tools -> Batch Rename -> String Substitution

Works very well.

I like to use this tool
http://www.bulkrenameutility.co.uk/Main_Intro.php

But better yet, if you are getting that '_copy' in your file names.. save it is photoshop WITHOUT that... it took a while to figure out when / why photoshop would add the _copy ending but it appears it does so when you are saving a TIF or PSD file as a jpg that otherwise couldn't be a jpg..

so, if the file has layers, or if it is in 16bit and you try to save it as a jpg, the 'save as copy' check box is automatically and forcibly checked.  If you flatten the image and make sure it is 8bit then you can uncheck the 'save as copy' box and it won't add the '_copy' ending.