I don't use Windows but I'm pretty sure you're not properly using that feature. Most likely you're searching filenames rather than file content. There must be a flag that controls that somewhere.
Furthermore, you should use a decent text editor to search for files or even better, a PHP IDE, such as PHPStorm, NetBeans, Eclipse, etc. Performing a search with those tools it's a cinch and quite fast.
For example, the "ranked" search yields this results for me:
As you can see, the file is lang/qa-lang-profile.php, line 72.
Regarding "Click to vote down" it is in lang/qa-lang-main.php, line 195.
Anyway, in order to translate, it is much better to follow these steps than modifying that file: http://docs.question2answer.org/translate