NOTE: (03/12/2018) Nicole Birgel in the fb forum suggested:
- do not to use “Quick Format”
- do a “Full Format”
- FB user Dean Le Blanc recently reported success with this method:
- https://www.facebook.com/groups/209280506324242/permalink/330439800874978/

I'm somewhat reluctant to share the Windows10 way of doing this, as I found it far too fiddly, and with so many steps, it increases the likelihood for making mistakes and accidentally trashing your hard-disk rather than fixing your USB stick!

Please consider the Use a 3rd party formatting tool approach rather than this, as I feel most people will find it far more straight forward.

Anyway, for what it's worth, here goes…

• Windows has a GUI-based partitioning tool called “Disk Management”, but one drawback of it is that it does not permit the removal of volumes/partitions from removable-drives such as USB sticks.
• So for this 'volume/partition removal' step, I had to resort to a command-line tool called “diskpart”
• For the creation of new partitions on the USB stick, I jump back to the GUI-based “Disk Management” tool

• Click the “start” button and type “cmd.exe”
• Right-click it and select “Run as administrator”
• Run the command diskpart
• Do the list disk command to assess which disk equates to your USB stick

  Disk ###  Status         Size     Free     Dyn  Gpt
  --------  -------------  -------  -------  ---  ---
  Disk 0    Online          238 GB      0 B        *
  Disk 1    Online           15 GB      0 B

• Ok, for me, I know my USB stick is about 16GB, so I know it is Disk 1
• So I type “select disk 1”
• Next, I need to figure out which partition I want to delete
• So I type “list volume”

  Volume ###  Ltr  Label        Fs     Type        Size     Status     Info
  ----------  ---  -----------  -----  ----------  -------  ---------  --------
  Volume 0     C   Windows      NTFS   Partition    195 GB  Healthy    Boot
  Volume 1     D   LENOVO       NTFS   Partition     25 GB  Healthy
  Volume 2         SYSTEM_DRV   FAT32  Partition    260 MB  Healthy    System
  Volume 3         WINRE_DRV    NTFS   Partition   1000 MB  Healthy    Hidden
  Volume 4         LENOVO_PART  NTFS   Partition     15 GB  Healthy    Hidden
* Volume 5         NEW VOLUME   FAT32  Removable     15 GB  Healthy

• I think it is Volume 5, as that is 15GB… But I'd like to be more confident of that…
• So I type “select volume 5”
• Then I type “detail volume”

  Disk ###  Status         Size     Free     Dyn  Gpt
  --------  -------------  -------  -------  ---  ---
* Disk 1    Online           15 GB      0 B

Read-only              : No
Hidden                 : No
No Default Drive Letter: No
Shadow Copy            : No
Offline                : No
BitLocker Encrypted    : No
Installable            : Yes

Volume Capacity        :   15 GB
Volume Free Space      :   15 GB

• Aah good, I get some assurance early on that Volume 5 exists on Disk 1, my USB stick!
• Now to delete this volume, I type “clean” (WARNING: be 100% sure you've selected the correct volume, as this will delete it!!)

Ok, I've now successfully deleted the sole partition off my USB stick.

• Click the “start” button and open the “Disk Management” by right-clicking and “Run as administrator”
• The USB stick's drive space should now show as being “Unallocated”

• Now right-click Disk1 and do “New Simple Volume…”

• A wizard appears, I click “Next”
• I accept the suggested volume-size and click “Next”
• I accept the default drive-letter and click “Next”
• I change from “NTFS” to “FAT32” and click “Next”

I am then finally rewarded with a single-partition FAT32 drive containing an MBR (confirmed via dd+hexdump).

Once the format is complete, copy your “THEC64-drive8.d64” file across and try it on your c64 mini.

If problems persist, let us know in either the community forum or the facebook group.