How do you reset a USB flash drive back to factory settings?

lx07 said:

Usually they are mbr partition table (not gpt), FAT32 and usually not marked active (active means a legacy BIOS based PC will boot it).

I'd make sure they are mbr not gpt, drop the "quick" so as to write zeros over the disk and not mark them active. Like this:

diskpart
list disk
select disk #
clean
convert mbr
create partition primary
format fs=fat32 quick
active
exit

Hi again, I got a call from Sandisk today about a separate issue..they were just confirming a question I'd asked about their USB 3.0 drives and if they are 100% backwards compatible with USB 2.0 ports. They confirmed they are.

During the conversation I told him I'd recently reset a USB flash drive back to factory settings and quoted the commands that you gave me listed above that I'd used ( Actually I used Diskpart down to the "convert MBR" command and completed the task in Disk Management (create a new simple volume, full format to fat32 etc).
He said that Sandisk ship their flash drives from the factory with an Active partition. He also said that in order for it to work correctly all the commands are perfect but I should type in "Active".
I told him that I was using a 2015 UEFI bootable laptop not a Legacy BIOS PC. He said that doesn't matter the flash drive should still have an Active partition. He asked me to look at the flash drive in Disk Management. I confirmed it said it had a Healthy partition but it didn't say it was Active beside where it said it was Healthy. I also said that a right click on the drive showed a Mark Partition as Active option which isn't selectable..its greyed out. I haven't seen it shown as selectable on any of my flash drives. He didn't have any idea at all why the Mark Partition as Active option was greyed out. Can you shed any light on that?
He said it seems like its set up correctly but he doesn't understand how without me having entered the "Active" command in Diskpart. He said that somehow Disk Management must have made it Active even though it doesnt state that it is Active on the partition?
You seem very knowledgeable on this subject so I wondered if you might be able to explain it to me

sportsfan148 said:

Hi again, I got a call from Sandisk today about a separate issue..they were just confirming a question I'd asked about their USB 3.0 drives and if they are 100% backwards compatible with USB 2.0 ports. They confirmed they are.

During the conversation I told him I'd recently reset a USB flash drive back to factory settings and quoted the commands that you gave me listed above that I'd used ( Actually I used Diskpart down to the "convert MBR" command and completed the task in Disk Management (create a new simple volume, full format to fat32 etc).
He said that Sandisk ship their flash drives from the factory with an Active partition. He also said that in order for it to work correctly all the commands are perfect but I should type in "Active".
I told him that I was using a 2015 UEFI bootable laptop not a Legacy BIOS PC. He said that doesn't matter the flash drive should still have an Active partition. He asked me to look at the flash drive in Disk Management. I confirmed it said it had a Healthy partition but it didn't say it was Active beside where it said it was Healthy. I also said that a right click on the drive showed a Mark Partition as Active option which isn't selectable..its greyed out. I haven't seen it shown as selectable on any of my flash drives. He didn't have any idea at all why the Mark Partition as Active option was greyed out. Can you shed any light on that?
He said it seems like its set up correctly but he doesn't understand how without me having entered the "Active" command in Diskpart. He said that somehow Disk Management must have made it Active even though it doesnt state that it is Active on the partition?
You seem very knowledgeable on this subject so I wondered if you might be able to explain it to me

It seems to be a bug in Windows 10 version 1803 that Active is greyed out in disk management. If you want to mark the USB flash drive partition active you have to do it with diskpart.

The ONLY time the active flag makes any difference at all is if you want to boot a legacy BIOS system from that partition.

NavyLCDR said:

It seems to be a bug in Windows 10 version 1803 that Active is greyed out in disk management. If you want to mark the USB flash drive partition active you have to do it with diskpart.

The ONLY time the active flag makes any difference at all is if you want to boot a legacy BIOS system from that partition.

Hi Navy, That was my understanding that the Active flag only makes a difference if you want to boot a Legacy BIOS system I told Sandisk Tech support that I didn't mark the partition as Active because my laptop is UEFI boot but he argued saying you should still set the partition as Active in Diskpart in order for it to work. Was I correct or is there something Im missing?

Bree said:

It's more subtle than that - and it applies to all disks, HDDs as well as USBs.

If a partition is Inactive I see 'Mark Partition Active' in Disk Management (1803), it's not greyed out and it will make the partition Active. It's when the Partition is already Active I see 'Mark Partition Active' greyed out.

Interestingly, on a Win7 PC I have to hand it behave exactly as described above for HDDs, but is always greyed out for a USB (active or not).

Hi Bree. As you can see on my UEFI boot laptop ..I haven't marked the partition as Active in Diskpart but Mark Partition as Active is greyed out. So whats happened in my case? Im running Windows 10 1803 fully updated. On a UEFI system do I need Active partition to be set or not? I was under the impression that USB flash drives were shipped and factory set without an Active partition but the Sandisk guy said theirs are shipped as Active so now Im not so sure. Im not too sure how knowledgeable the Tech Support guy was

sportsfan148 said:

Hi Bree. As you can see on my UEFI boot laptop ..I haven't marked the partition as Active in Diskpart but Mark Partition as Active is greyed out. So whats happened in my case? Im running Windows 10 1803 fully updated. On a UEFI system do I need Active partition to be set or not? I was under the impression that USB flash drives were shipped and factory set without an Active partition but the Sandisk guy said theirs are shipped as Active so now Im not so sure. Im not too sure how knowledgeable the Tech Support guy was

I see the exact same behavior on my UEFI system. The partition is not active and "Mark Active" is greyed out in disk management.

Again, the only difference it makes whether the partition is active or not is if you want to boot a legacy BIOS computer (or CSM mode on UEFI) from that partition. Other than that, it completely, absolutely does not matter. Data only partition does not matter if active or not. Booting in UEFI mode does not matter if active or not. Having it marked as active won't hurt anything, though.

NavyLCDR said:

It seems to be a bug in Windows 10 version 1803 that Active is greyed out in disk management. If you want to mark the USB flash drive partition active you have to do it with diskpart.

As was suggested on another thread it seems that the Mark Partition As Active option might be intentionally greyed out on Windows 10 (rather than it being an 1803 bug) when its a UEFI system because an Active partition is never going to be required on a UEFI system.