Renaming a group of files

Today I needed to do a mass replacement of file extensions to a different extension, this is very painful to do in Windows from anything I could see.
In the past I’ve used DIR to get file names and then excel to create a bat file of ren to be able to be expanded to every file, very painstaking.
Today i decided I would use powershell, should be alot easier, started looking up how to do it and instead found: ReNamer by Denis Kozlov. This tool gave me what I needed within seconds! It’s free for personal use, paid for commercial (don’t know how much there’s only a contact form about it). It lets you set up rules to do all kinds of things, I only need a very trivial setup, 1 rule “replace foo with bar” and to uncheck ignore extensions.
It even gives you a preview of the intended changes!