Ok, this trick won't produce anything quality, but hey we're talking about free, right? Well, as long as you can record from a player such as Winamp, and you have some percussion samples, here's what you can do:
You link up the samples in a usable order (you could actually arrange an entire loop if you create shortcuts to specific samples and just line them up). Then, you highlight the first one, put your right fingers on the arrow keys of your keyboard, and use the "enter" key with you left hand to play. Now, start recording from your player, such as Winamp, and use the arrows to navigate through the samples and play them with the enter key. Basically, works similar to a keyboard, but of course without the speed? Lol... that is about as free as you can get...
Found this when I was just messing around with the samples on my Magix CD.
-speculative