Us UNIX folk have been using grep since the flood, but there's hope for you poor Windows folk.
Grep for Windows
Get ready for a whole new free finding experience!
Mac
PS: BareGREP -
Bare Metal Software > BareGrep - Free grep for Windows - offer a free GUI version if you don't mind a splash-screen. JGSoft's PowerGREP -
Powerful Windows GREP - is the best, but you have to pay for it...