Below are free things I’ve found on the internet and use frequently.
ReNamer – Batch file renaming
A software utility that I have found useful for renaming my photographs after transferring them from my camera to my PC is called simply “ReNamer” [download] Often the files start with “_MG” instead of “IMG.” Since I typically take several hundred photos on vacation, trying to rename them manually, one at a time is tedious to say the least. I found this utility at PC World almost two years ago and have used it extensively ever since. It is virus free and simple to use. PCWorld.com is a safe place to download from, at least, I have never had a problem in twenty years of downloading from their site. Once I reached 9999 photos with my camera, it started over at 0001. I used this utility to insert a “1” so that the name would be “IMG_10001” instead of the duplicate name “IMG_0001.” I am now over 20,000 photos and so insert a “2.” Although I keep my photos in folders by date, I want to avoid any possible ambiguity should I try to gather photos from different folders into one slideshow or other type of image display.
This is just how I use it, of course. If you decide to download and use it, I would like to know if you find it useful and how you have decided to use it.