SzymekRak:
The Original Mighty 1284p bootloader doesn't work and Nick Gammon's sketch doesn't want to compile on Arduino IDE 1.0.1.
Please post your error messages. Possibly you didn't install the SDFat library. There is a comment near the top of the sketch about that:
// for SDFat library see: http://code.google.com/p/beta-lib/downloads/list
#include <SdFat.h>