Protools L.E is actually free, you need to buy an Mbox in order for it to work though. the Mbox comes with a protools ignition pack, with a cd for L.E. Protools doesn't configure to any other hardware besides Digidesign hardware.
Cheapest way in is to look at the M-Audio designed protools ( M-powered) or one of the cheaper Mbox's like the Micro or Mini. I'd recommend the Mbox setup, as i haven't had experience with the M-Audio Protools.
If you are downloading anything off the net for free using no hardware, it is not protools.