For months I have been grappling with the problem of using cards larger than 4GB in my G11 which does not allow the firmware update method of creating 2 partitions and loading CHDK and also because sdminste.exe does not work with my Sandisk card reader/Windows Vista setup. I have finally found a solution and thought I would post it here in case someone else has the same problem.
You will need to download a partition manager like MiniTool Partition Wizard Home edition (free) which can be found here
http://www.partitionwizard.com. Make sure you have loaded your SD card and that you have selected the correct disk in the Partition Manager Window. There is a safeguard in that no action is taken until you select apply but be careful not to remove the partition(s) on your computer's hard drive. After removing the current partition, make two new ones, the first should be as small as possible (8MB in this program) and formatted in FAT. Label this partition CHDK_SMALL. Format the rest of the card as the second partition in FAT32 and label it CHDK_LARGE.
Since Windows only recognises the first partition of removable media like SD cards you need to change the driver for your card reader following the instructions found here
http://chdk.setepontos.com/index.php?topic=2332.msg21520#msg21520 making sure you use the "have disk" option which is only found when you select "Browse for driver software on your computer" and then"Let me pick from a list of drivers on my computer" and in the next window the "have disk" option is available (in Vista)
Windows will now recognise and be able to access both partitions as separate drives.
You now need to make the first small partition bootable using Windows Method #5 and the EOSCard utility found here
http://chdk.wikia.com/wiki/Bootable_SD_card. I had to do this in a different card reader/slot on another computer because EOSCard no longer recognised my card reader/card as removable media because of the new driver. You only need to check the bootable option in the utility since the card has already been formatted.
Put the SD card back in your adjusted card reader and download the full version of the CHDK build for your camera and unzip it to the first small partition/drive CHDK_SMALL on the the card. Now you can remove the card, lock it, insert it in your camera and start in playback mode and CHDK loads as it does for a 4GB card.
I have used this method with Sandisk Ultra 8GB cards, a Sandisk cardreader and Vista Home Premium.
