BelchX is a port of an old System 7 extension for the Mac, called Belch. BelchX is an invisible application that will cause your Mac to have a case of indigestion: it lets out a nasty belch every once in a while. Put it on your friends' Maces, and they will love you for it.
If you wish to quit BelchX, simply open up a Terminal window and type:
killall QUIT "Belch"
If that doesn't work, simply choose "Log Out" from the Apple menu, then log back in.