How do I fix my SD card after it was split into multiple drives by Windows loT core?

Solution 1:

The Disk Management tool may not let you work on SD cards and flash disks with partition tables. diskpart will work, though.

1. Open the Start menu, type diskpart and press Enter. You may have to confirm UAC prompt.
2. Type list disk Enter. Take note of card's disk number.
3. select disk X Enter (X is disk number from previous command.
4. clean Enter - this will overwrite partition table with zeros - all data will be lost.
5. Use Windows Explorer to initialize the SD card/flash disk.

Solution 2:

Firstly, you need to run diskmgmt.msc - if you have Windows 10, just click start, then type "diskmgmt.msc", right click it, choose to start it as administrator. You should get something like on the screenshot below. Then you just right-click every volume on your sd card, and delete it. After you deleted them all, you can create one also by right clicking on empty/unassigned space on sd representation.