grepWin has been around awhile. I ran across it looking for an easy way to replace text in my Readme.txt files. This tool is easy to use. I'm not a RegEx wiz. But it has a nice RegEx test feature. Paste some sample text from one of the files you want to change and see if your RegEx does the job before hitting the Replace Button.

It also has a feature to create backup files for each file in which it replaces text. It made what could have been a real chore lasting over an hour into about 10 minutes work. Very nice.

It has .msi installers for both 32 and 64 bit. It installs as an Explorer Context Menu Extension. It worked fine for me in W8. No mumbo jumbo. Just install and use.