Extract all the files(and folder) directly to the root of your C drive.

2) Place whatever dol file you want to boot into the my_bootable_disc folder located in the root of your C: drive, and rename it to bootldr.dol. Also place a file in the same folder that is at least 500MB. It doesn't matter what it is, it's just for padding.

3) Double click on the BootableDisc.bat file.

4) Wait until the process is complete, and then burn the gcdisc.iso that has been created in the root of your C: drive.

5) Put the disc into the gamecube and boot it.

Enjoy!