You can use MPC-HC to play blu-rays, but it's rather clunky. I believe you have to open up the M2TS file for the movie manually within the player because it doesn't support the blu-ray menus.
Do you have AnyDVD HD? If so, you can rip the movie to the hard drive and mux the movie and audio track into an mkv container and play it through Windows Media Player. You'd need a lot of hard drive space though. And AnyDVD HD isn't free.
I suggest you just pony-up and purchase either Arcsoft's TMT3 or Cyberlink's PowerDVD to play your blu-rays.