Starting from version 4.6, GAG has a facility that allows third-party
programs to locate and change the configuration data. To do it, you must 
have access to the first 63 sectors of the boot hard disk. The first one
contains the MBR and the first stage, and the other 62 contains GAG itself.
Load the laters and search the string CONFIGDATA (in uppercase). That
string is located AFTER all the configuration data, so you will be able to
change it and store again the sectors.