I have looked thorugh my motherboard manual on this issue, but it doesn't mention anything specific about this, so I'm left a little confused.

My main PC has a MSI MPG Z390 Gaming Edge AC motherboard. I have 2 m.2 SSDs installed in it (one with Linux and one with Windows). I also have a third m.2 SSD installed in a USB adapter enclosure:

https://www.amazon.com/dp/B07MNFH1PX?th=1

I believe the SSD in the USB enclosure is SATA-based.

If I plug the USB m.2 adapter into my PC while my PC is running, it recognizes the drive as expected, and all is good. However, if I leave the USB adapter plugged in (which I'd like to do), then when I reboot or power on my PC, the motherboard says one of the m.2 SSDs on the motherboard is not available (and it always seems to be the same one).

The motherboard manual does talk about the fact that some of the SATA ports will be unavailable when both m.2 slots are used, though it doesn't mention anything about USB devices affecting the m.2 slots on the motherboard. I've done some searching online, and it sounds like it may be due to bandwith sharing, and perhaps the motherboard is disabling that m.2 SSD on the motherboard for some reason, but I'm still not entirely sure if that's the case and if there's a BIOS setting I might need to change that would prevent the USB adapter from interfering with the m.2 SSD on the motherboard.

Has anyone seen a situation like this?

Nightfox

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On 04 Feb 2026, Nightfox said the following...

If I plug the USB m.2 adapter into my PC while my PC is running, it recognizes the drive as expected, and all is good. However, if I leave the USB adapter plugged in (which I'd like to do), then when I reboot or power on my PC, the motherboard says one of the m.2 SSDs on the motherboard is not available (and it always seems to be the same one).

i found one other model device with the same chipset and there are a few reviews that suggest disabling usb booting.

my guess is your motherboard thinks it's 'helping' by disguising your usb enclosure as one of it's own (maybe that helps someone out there who wants to boot windows from usb?)

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Re: USB m.2 SSD adapter interferes with m.2 drive on mobo
By: Nightfox to All on Wed Feb 04 2026 04:59 pm

Has anyone seen a situation like this?

Yes... but only with Windows 11. And not exactly what you are describing but this:

I have one Windows 11 PC (not by my choice) and three NAS devices connected to it. Every now and then, a NAS device will disappear from the Win 11 PC. I also have a few Win 10 PCs and one Win 7 PC and the NASes never disappear from the others... only the Win11 box.

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Re: USB m.2 SSD adapter interferes with m.2 drive on mobo
By: Bf2k+ to Nightfox on Thu Feb 05 2026 03:11 pm

Has anyone seen a situation like this?

Yes... but only with Windows 11. And not exactly what you are describing but this:

I have one Windows 11 PC (not by my choice) and three NAS devices connected to it. Every now and then, a NAS device will disappear from the Win 11 PC. I also have a few Win 10 PCs and one Win 7 PC and the NASes never disappear from the others... only the Win11 box.

This is before my PC even boots into the OS. The issue is that when that USB drive is plugged in when my PC boots up, the boot drive (which is one of the m.2 SSDs) appears as no longer available, so it can't boot into the OS.

Nightfox

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Re: USB m.2 SSD adapter interferes with m.2 drive on mobo
By: Nightfox to Bf2k+ on Thu Feb 05 2026 03:40 pm

This is before my PC even boots into the OS. The issue is that when that USB drive is plugged in when my PC boots up, the boot drive (which is one of the m.2 SSDs) appears as no longer available, so it can't boot into the OS.

Yes... I realized after I left the reply that it wasn't applicable to your issue... sorry about that.

I guess I was just in a 'shit all over Win11' mood...

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Re: USB m.2 SSD adapter interferes with m.2 drive on mobo
By: Nightfox to All on Wed Feb 04 2026 04:59 pm

the drive as expected, and all is good. However, if I leave the USB adapter plugged in (which I'd like to do), then when I reboot or power on my PC, the

While I haven't had specifically the same issue, I have indeed had plenty of various issues when leaving USB things connected and rebooting. In general, USB is absolute garbage. It's barely fine for HID (keyboard, mouse, etc). It's definitely improved over the years, but improved garbage is still just that. USB-C is almost getting there, adding a lot of features but I dunno if it's improved in leaps and bounds in stability/reliability. Anyway, my suggestion is not to expect USB drives and other complex devices not to goober your USB things on reboot. Janky busses, janky OSes, janky drivers.. not a great combination. Unplug, reboot, replug. On unexpected reboot, pray.

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Re: Re: USB m.2 SSD adapter interferes with m.2 drive on mobo
By: fusion to Nightfox on Thu Feb 05 2026 01:47 am

reviews that suggest disabling usb booting.

my guess is your motherboard thinks it's 'helping' by disguising your usb

Good call.

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Re: USB m.2 SSD adapter interferes with m.2 drive on mobo
By: phigan to Nightfox on Mon Feb 09 2026 07:49 am

the drive as expected, and all is good. However, if I leave the USB
adapter plugged in (which I'd like to do), then when I reboot or power on
my PC, the

While I haven't had specifically the same issue, I have indeed had plenty of various issues when leaving USB things connected and rebooting. In general, USB is absolute garbage. It's barely fine for HID (keyboard, mouse, etc). It's definitely improved over the years, but improved garbage is still just that.

Considering that USB has been around for a long time now, I'd think it would be better.

USB-C is almost getting there, adding a lot of
features but I dunno if it's improved in leaps and bounds in stability/reliability.

Isn't USB-C just a different type of connector for USB? You can buy adapters to plug USB-C into USB-A and vice versa (and same with USB-C to micro USB). I'm unclear on what you mean by USB-C adding features.

Anyway, my suggestion is not to expect USB drives
and other complex devices not to goober your USB things on reboot. Janky busses, janky OSes, janky drivers.. not a great combination. Unplug, reboot, replug. On unexpected reboot, pray.

That's a bummer. I've actually never had this problem before with a USB device, but I think this is the first time I've tried leaving a USB storage drive attached to my PC.

Nightfox

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Re: USB m.2 SSD adapter interferes with m.2 drive on mobo
By: Nightfox to phigan on Mon Feb 09 2026 08:14 am

Isn't USB-C just a different type of connector for USB? You can buy adapter to plug USB-C into USB-A and vice versa (and same with USB-C to micro USB). I'm unclear on what you mean by USB-C adding features.

Yes, but it's also more bandwidth and has all kinds of fancy new negotiation. Like all the different power options that can go through it, etc. It's not just 4 pins (5v, Rx, Tx, Gnd) anymore. Not sure how much the code/drivers for the USB busses has changed to accomodate for the newly expected uses and fuctionality.

But yeah, most of the time you leave the drive plugged it, it should be fine. In my experience, though, it's not unheard of for it to either not show up or muck up the drive order or some other such weirdness on reboot.

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