Question For Guitar Players

I was thinking of getting a Tascam Portable Guitar Trainer ($150 & $25 for an AC Adapter), which loops whatever part of a song you want to learn. It also slows down a song up to 50% without changing the pitch. My brother said he thinks there's software that can slow down a song ever more, but he doesn't know the name of the company/s. I was hoping you guys could recommend whatever it is that you use, or have used.

Thanks

P.S. Is there free software available???