A:
From researching on your Nikon D80, the max capacity that it allows is only up to 32GB. Any more and the system has a hard time using it. You can try to format the SD card to read as FAT32 with SD Formatter (a formatting service used for any SD card to clear/clean cards) and hope that it reads all 64GBs. Looking around more, some people have stated it works, where most have said that it does not. Nikon D80 will see SDHC (up to 32GB capacity) chips and not SDXC (beyond 32GB capacity. IE: 64GB, 128GB 256GB cards).
I would stick with 32GB SDHC cards for your camera and not 64GB SDXC.
Though if you would like to try the FAT32 format trick, you can download the file from their site at
https://www.sdcard.org/downloads/formatter_4/
Capacity capabilities list:
https://www.flickr.com/groups/18181418@N00/discuss/72157633839899792/
https://www.ifixit.com/Answers/View/141523/FULL+message+on+LCD
as well as their manual that comes with the camera!
If this works, have fun with your card! If not, I would find another use or return the chip for another 32GB SDHC card.
Hope all the info has helped out!!