I found a Music Slow DownSoftware that is so good I must rave about it. It has the user interface that I have for a long time wished for in a software like this. It automatically loads all of your music for slow down and looping. When I add new songs to learn, it automatically loads them the next time I open the software. Awesome product called mTrax by www.TerraSofta.com
You could also use Guitar Pro or Powertab to do the same thing. I like Guitar Pro because it has a speed trainer, that loops the music over and over and you can control the interval by which the tempo is increased.....you can actually play at 100% speed without even realizing you did it!