Hello Gypsy,
If you're unable to format your SD card from File Explorer, I recommend using the Disk Management tool. Please make sure that you're signed in as administrator before following these steps:
- Right-click the Start button.
- Select Computer Management.
- Go to Storage > Disk Management.
- Right-click your SD card and select Format.
- Enter the Volume label, set the File system, and select the check box for Perform a quick format before clicking OK.
- Click OK again to complete.
Let me know how it goes.