If you want a GUI tool, I like GrepWin[0] - you can have it install an Explorer context menu item, right click, hit GrepWin, then you can search. Supports simple text searches as well as regex. You can filter by filesize too. Been using this for years, really useful tool.
On the command line, I just use grep (a cygwin version of it, installed with Git for Windows, I think).
On the command line, I just use grep (a cygwin version of it, installed with Git for Windows, I think).
[0] https://tools.stefankueng.com/grepWin.html