The following info may or may not help someone else with similar issues to myself.
I came to this thread looking for an answer to why I could not access my 64GB microSD card (replacement from SANDISK) on any of my android devices despite reformatting to FAT32 (using HP USB Disk). Card originally was exFAT.
I used the suggested formatting tool SD Association’s Formatter from this thread and also selected the Format Size Adjustment option as ON with a quick format.
My card was then recoqnised in my Android devices (Toshiba AT300 & Samsung Galaxy SII).
The tool had set the file system back to exFAT.
Here is a snippet from the tools manual:
_ Format Size Adjustment _
If the formatted capacity of the card is not a multiple of capacity in a cylinder, some hosts may not
access the card successfully. This option adjusts formatted capacity to a multiple of capacity in a
This option does not adjust the formatted capacity. Usually, this option should be selected.
This option adjusts the formatted capacity to a multiple of capacity in a cylinder. This option may
reduce the formatted capacity.
This option should be used by specific users who encountered a trouble with formatted capacity.