As far as I understand, the A720is being a "Dry OS" camera does not have the "load firmware" command that the other cameras use (*.fir file?).
The only option is to load the A720is through booting (will boot correctly both in shoot or playback mode). And, booting only works when the SD Card is formated FAT 16 (2 GB and under, normal format command). For a 4 GByte SDHC card, you need to format it with the non-standard extra large cluster size... Not guaranteed to be compatible with all programs/devices--but does work on my A720is, and the Sandisk card reader/Windows XP.
To format with FAT16
format x: /fs:fat (where x: is your drive letter)
then
bootable x: (again, where x: is your drive letter)
then
copy DISKBOOT.BIN file to x:\
Write protect card to boot into CHDK and install into your camera... Just turning on the camera should display your CHKD splash screen.
As I understand, formating an 8+ GB SDHC card with the ":fat" command will leave you will a 4 GB card capacity. If you look around here, you can find people that have figured out how to make a 8GB SD card with multiple partitions--but it is non-standard and may not work with most standard USB/OS mounting programs (will only see first partition).
One problem I experienced on with the first version of CHKDSK for the A720is with 4G SDHC was that the CHDK directory structure (Scripts, Lang, etc.) sub-directories where not created and therefore I could not save my CHDK configuration configuration. But the newer versions seem to work fine.
-Bill
