I don't get it, what's exactly your question? do you already have a Linux installed or you want to install linux?
If you want to install Linux just get any distribution you like for free online, i recommend the debian based distributions like knoppix, Ubuntu or Debian.
But, if you had a linux installed, then you installed windows and you want to recover the linux sesion because always that you turn on your PC it start windows, you should try with the installer of linux again and install the Grub or Lilo, or use the live Cd and go to the Lilo.conf or grub.conf, agree your windows session and configure all your boot parameters as you want it.