It's a windows 7 (64 bit) computer.
Strange. That should work fine and has for me in the past.
If you run WICKS or sdminste.exe, do you have the SD card lock switch in the "unlocked" position?
Once you have run WICKS or sdminste.exe to swap to the larger partition, (even if it does not appear to work on your PC) will that SD card still autoboot CHDK? Or does it say "Card Locked" when you boot?
Or is this something weird about needing to umount and remount the card - or reboot the PC - after WICKS or sdminste.exe swaps the main partition.
If I use the firmware update method do I need to reconfigure my SD card?
You don't need to reconfigure. You used STICK so it should have put the
ps.fi2 file needed for "firmware update" booting on both partitions in the home (root) directory. That will allow "firmware update" booting regardless of the currently active partition. If there is no ps.fi2 file in the root of the large partition, you need to copy one there from either the small partition or by extracting from the downloaded CHDK install file.