If the command you have run is the one given in the Chameleon Read Me file, then your GUID partition table is still intact. The reason for this is that this command only overwrites the master boot record (MBR), which comprises the first 446 bytes of sector 0. The MBR partition table takes up the last 64 bytes of sector 0 and should not have been affected by this command. The GUID partition table only starts in sector 1, so it won't have been affected by that command either. If this sounds complicated, go to wikipedia and read about GPT and MBR.