As cmh stated, try it in your phone first. That should work.
If not, sdformatter should work. Did you get it from here ->
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All 64gb cards come pre-formatted as exFat which not all smartphones can read, including the Droid HD (XT925/XT926).
i'm using a 64gb card in my phone. Have been since I had a Droid RAZR MAXX (XT912) and it works like a charm. I used sdformatter to format the card because I believe my RAZR MAXX couldn't format it so I had to use sdformatter.
In sdformatter, I believe you need to set the format size adjustment to on to adjust the cylinder count.
Last resort is to use the following tool ->
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This will allow you to format a partition > 32gb as fat32. Normally, you can't do that (NTFS is what you normally would use), but this tool will allow it.