define free............ ?

Unfortunately to get anywhere near a decent drum sounds in any software requires downloading many Gigabytes of samples

I would recommend getting the sfz soundfont player

http://www.project5.com/products/instruments/sfz_player/default.asp
or
http://www.kvraudio.com/get.php?mode=show&id=769

There are many soundfonts. nskit used to be free, but I see they are commercial only now http://www.naturaldrum.com/

The easyrider kit is pretty awesome for a free soundfont.
http://www.michaelkingston.fi/kingstondrums/easyrider.html

If you want to pay a few bucks (about R135) for the computermusic magazine, you will find many a drum sampler with lots of great sounds on the DVD.

hydrogen is free and very , brought to us from the linux boys