changing bitrates on mp3's?

Hey i got a nice collection of mp3's, but most of them were ripped (taken from music cd saved as mp3's) at 192 kbps. I just got an mp3 player, and i want the music to take up less space, so how could i change all of the bitrates to 128 kbps? any programs, freeware, that can do this? thx.
I know you can't go from a lower bitrate to a higher, but I am not sure about the reverse. I would just try to re-rip them at a lower one.
WMA Advanvced Workshop maybe can do it, but what your asking is so common, so it should be hundreds of programs like that.
because you only want to get 192kbps to 128kbps.

Maybe its something usefull here -->
so confused...
ghost dogg, I've been directed to a lot of other of the LAME sites (couldn't find way around the pun) but confused how to actually work it. I've gone into a lot of pages, downloadd 2 different thing, and the .exe file doesn't work in either, which is really confusing ?:(

could someone help me out here, explain where to go, what to do, or should i just burn all 200+ mp3's to cd's and rip them again at 128