If the microSD card is unreadable through a peripheral device, the card may use an incompatible file system, such as NTFS, or it may not be formatted at all. Data corruption could also be the culprit.

See this Amazon review on Sandisk 32GB microSD card. I learned something very useful as it relates to getting the most performance out of these microSD cards. - See particularly the criticizing ...

You can format your HDD, SSD, Memory Card, etc., using these free file system management tools or FAT32 format tools. Windows File Explorer is the default option you can use to format a drive in FAT32 ...

- Stops at a limit of 4 Gb for file size System Hierarchical = slower (cause of permissions) - and supports 4+ Gb file size So ummm.. what's true here..? for your basic microsd you have to choose for ...