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Windows does not remember SD card drive letter

Originally asked at Lenovo forums because I've only ever witnessed this weird behaviour on my newly-acquired ThinkPad T480. But possibly something wrong with the OS instead of hardware.

https://forums.lenovo.com/t5/ThinkPad-T400-T500-and-newer-T/Windows-does-not-remember-drive-letters/td-p/4449492

I had for years previously been using Microsoft Surface Pro 4, with a micro-SD card slot that can be coveniently named A: to make it look like a floppy drive.

Now as I transition to the ThinkPad T480, I slot in the SD card and named it A: as well. But everytime I restart the whole system, the Windows in this laptop totally forgets the assignment and names it D: If I try another letter like E: it still reverts to D: on reboot.

Is there something wrong with this copy of Windows 10, or something about the communication between BIOS and OS that got lost in translation that the SD card slot in the laptop is indeed the same?

I tested plugging in a USB hard disk, named it D: while the SD card gets E: on reboot, the SD card becomes D: while the hard drive is forced to E: There seems to be some sort of "sorting order" happening in hardware that Windows cannot keep track of?

Hi icelava

My name is Andre Da Costa; an Independent Consultant, Windows Insider MVP and Windows & Devices for IT MVP. I'm here to help you with your problem.

Try disabling fast startup to see if the drive letters stick.

Press Windows key + X
Click Power options
Click Additional power settings under Related settings
Click Choose what the power button does
Click Change settings that are currently unavailable
Uncheck 'Turn on fast startup (recommended)

Click Save changes.

Click Restart now and see if it works.
Best regards,
Andre Da Costa
Independent Advisor for Directly

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Try disabling fast startup to see if the drive letters stick.

Press Windows key + X
Click Power options
Click Additional power settings under Related settings
Click Choose what the power button does
Click Change settings that are currently unavailable
Uncheck 'Turn on fast startup (recommended)

Click Save changes.

Click Restart now and see if it works.

The Additional power settings - which goes back to traditional control panel Power Options - does not have a "Choose what the power button" does option. At the point the UI offers the selection of which power plan to use. The ThinkPad T480 offers

  1. Balanced (active)
  2. Airplane
  3. Timers off (Presentation)

If I channel deeper into that plan, all the Power buttons and Lid > Power button action offers are

  1. Do nothing
  2. Sleep (active)
  3. Hibernate
  4. Shut down
  5. Turn off the display

There is no fast-startup option. In fact I've never seen such a behaviour offered from any other computer I've worked with.

Scratch the previous observation I thought it was in the plan settings; didn't realise there's a broader setting on the left side.

Nope, with Fast startup disabled the SD card still reverts to D:

The melody of logic will always play out the truth. ~ Narumi Ayumu, Spiral

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Press Windows key + X
Click Device Manager
Expand Disk drives
Right click the SD card
Click uninstall

Restart.

Check if you can change the drive letter, restart then check if it remembers.

I see some updates available for your make and model I recommend you apply.

BIOS Update May 2019
https://download.lenovo.com/pccbbs/mobiles/n24u...

Chipset Driver Update November 2018
https://download.lenovo.com/pccbbs/mobiles/n24i...

Card Reader Driver Update May 2019
https://download.lenovo.com/pccbbs/mobiles/n24x...

Note: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.
Best regards,
Andre Da Costa
Independent Advisor for Directly

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I have ran Lenovo Vantage yesterday to keep the system updated.

  • BIOS/UEFI - already v1.24
  • Realtek Media Card Reader - already v10.0.18362.32248
  • Intel Chipset Device Software - Mobile Intel(R) Processor Family I/O PMC - 9D21 - already v10.1.5.1 (interestingly the driver is dated 18 Jul 1968, nice)

I removed the SDXC Card device from Disk drives and it came back on reboot, still clinging on to D:

The melody of logic will always play out the truth. ~ Narumi Ayumu, Spiral

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Check if there is an option to reset the BIOS defaults.

Try resetting your BIOS defaults:

https://www.groovypost.com/howto/reset-pc-bios-...
Best regards,
Andre Da Costa
Independent Advisor for Directly

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Actually I don't even think it's a BIOS/booting problem anytmore. As reported in the Lenovo forums just now, I tested simply by popping out the card while assigned as A: and on re-insertion it became D: again.

There is some kind of communication breakdown between the card reader and OS, I suspect. Windows is unable to recognise it's the same card device.

The melody of logic will always play out the truth. ~ Narumi Ayumu, Spiral

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Thank you for the troubleshooting help anyway. I am requesting Lenovo techsupport; see if I can negotiate a device driver update to the card reader controller to avoid announcing "new drive" every time a card's slotted in.
The melody of logic will always play out the truth. ~ Narumi Ayumu, Spiral

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Please keep us updated and let us know how it goes.
Best regards,
Andre Da Costa
Independent Advisor for Directly

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After plenty of back and forth, Lenovo techsupport are of the attitude that having a random drive letter assigned is "normal behaviour", of which I have more than enough proof from my other computers/hardware to contradict their claim. But they absolutely don't want to take responsibility for (nor seemingly even want to investigate) the inner workings of the Realtek card reader. They're trying to push the blame to Windows, so I must now try to find a way to verify with Microsoft that it is indeed a hardware misbehaviour rather than an OS bug.
The melody of logic will always play out the truth. ~ Narumi Ayumu, Spiral

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Since Lenovo support is adamant it's Windows' fault, I engaged Microsoft premium support to help me look into the problem.

 

Oddly enough, the first suggestion to run a chkdsk on the card managed to let Windows remember the drive letter (A: ) across restarts and shutdowns. Does that mean Windows does not want to remember a card that was suspected to be "unclean"? It certainly never suggested before I ought to scan that card; there's no problem with it; and the card in fact came from my preceding Surface Pro 4 which never had this behaviour.

 

And the more confusing, mysterious issue - Windows can remember the drive letter on first removal/re-insertion, but the second time it'd forget and fall back to E: (C: and D: reserved for SSDs). On experimental tweaking of disabling the USB root hub devices' power management control, Windows can't even remember the drive letter on first removal. That makes the situation slightly worse. Power management needs to be enable to at least let Windows remember the drive letter the first time.

 

Microsoft support is currently just as confused as I am on what's happening between Windows and the card reader hardware.


Well at least the "better half" of the problem is resolved; I ought to be able to persist A: so as long as I don't physically eject the card.

The melody of logic will always play out the truth. ~ Narumi Ayumu, Spiral

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Last updated March 25, 2023 Views 1,457 Applies to: