It needs to be graphical. No sed, awk, grep, perl, whatever. I know how to use those and I do use them now, but I need to cherry-pick each replace in 300+ files.
I want
I use gVim for this task all the time. I open up all the files at once, then use the commands to perform a subsitution on each file, asking for confirmation. Generally I use < 20 files, so I open them as tabs and use this:
:tabdo %s/foo/bar/gc
gVim works fine on Windows :) My coworkers often use Textpad to do this same thing, but I'd say gVim is much more efficient at it.