XPS 8940, 3.5" SATA HDD not recognized

 Ensure that the SATA data cable connecting the new HDD to the motherboard is securely connected at both ends. Also, check that the power cable from the power supply unit (PSU) is connected properly to the HDD.

Try connecting the new HDD to a different SATA port on the motherboard. Sometimes, a specific SATA port might be faulty or disabled in the BIOS.

 Enter the BIOS setup utility and verify that the SATA port to which the new HDD is connected is enabled and recognized by the system. Additionally, check for any settings related to SATA devices or disk detection.

 Ensure that your Dell XPS 8940 has the latest BIOS version installed. Sometimes, BIOS updates include fixes for compatibility issues with hardware components. Additionally, check for any available driver updates for your motherboard and SATA controller.

 If possible, try connecting the new HDD to another computer to see if it's recognized. This can help determine if the HDD itself is faulty.

 Even if the HDD is not recognized in Disk Management, it's worth refreshing the disk list or rescanning for new hardware to see if the HDD appears.

Ensure that the new HDD is compatible with your Dell XPS 8940 system. Check the specifications of the motherboard and the HDD to ensure compatibility with SATA standards (e.g., SATA III).

If you've tried these steps and the new HDD still isn't recognized, it's possible that there may be a hardware issue with the motherboard or SATA controller.

Check bios>sata operation. If it is RAID, change to AHCI, save, exit bios.  Dell bios default is often RAID.

Then you need to do a few command line (see reference below) so pc can boot again.

https://superuser.com/questions/1280141/switch-raid-to-ahci-without-reinstalling-windows-10

First, you need to access your computer's BIOS settings. You can usually do this by restarting your computer and pressing a specific key (often F2, F10, or Del) as it starts up. Once you're in the BIOS, look for the SATA operation option. If it's set to RAID, change it to AHCI. Then, be sure to save your changes and exit the BIOS.
Thankyou...
This is Talha from thediversemark

"If it's set to RAID, change it to AHCI."  Same thing redxps said.  Truly amazing!!

@Dogs_Rule 

One idea I have and would do is format the SSD in another PC and see if that works.

And you have to change BIOS from RAID to AHCI in the right way or you'll make PC unbootable.

1. Open Cmd prompt window, run as administrator.
2. Copy-paste this command, which will start Windows in Safe Mode the next time you reboot: bcdedit /set {current} safeboot minimal and press Enter
3. Restart the computer and tap F2 to enter BIOS setup.
4. Change SATA Mode from RAID to AHCI.
5. Save the change and exit Setup.  Windows will automatically boot in Safe Mode.
6. Open Cmd again, as in step #1.
7. Copy-paste this command, which will start Windows in Normal Mode the next time you boot: bcdedit /deletevalue {current} safeboot and press Enter
8. Reboot and Windows will automatically start with AHCI drivers enabled.

Do we know yet what the BIOS is actually set to?

Dell ships PCs with SATA Operation set to RAID, even though the BIOS default setting is AHCI.

@RoHe​ You can also do shutdown.exe -r -fw from an elevated cmd prompt which will reboot directly into the uefi without having to press buttons. 

Thank you All for the help and suggestions. I did notice that in the BIOS it's set to RAID. I will try the suggestion made by @RoHe . My only "problem" right now is building up the courage to do it right, so I don't mess it up.

I will let you know how it goes.

@Dogs_Rule​ soon as ya do it and reboot to safe mode, it will just install the drivers right then and there. it's safe. Fast.

And if you're still worried, back up all personal files on the boot drive C: first.  Or better yet, create a complete image of the boot drive and save it on an external drive...

@RoHe​ 

So I'm trying your suggestion, but I am running into a problem right off the bat.

I'm running as "Administrator"

And then when I run the command:  bcdedit /set {current} safeboot minimal

I get an error:

Not sure what I am doing wrong.

@Dogs_Rule​ 

Is the new SSD plugged into a blue or black data port?  Not sure if that would make a difference, but something I would try.  White data ports are for other peripherals like DVD drives.  Not sure if you tried different data ports.

It sounds like at this point you may need to reload Windows.  As mentioned before by RoHe, make sure your important stuff is backed up first.

I don't know what other workaround there is with other stuff not working.

Change BIOS settings to AHCI.  Of course, it won't boot.  Reload Windows while in AHCI mode.  Make sure Secure Boot is on.  Make sure storage SSD is disconnected.

While reloading, delete previous partitions on the boot drive when the Window pops up asking what partition to load on.  Windows will automatically create the partitions to load on after clicking on Next/Install.

Very important - I believe the 8940 was introduced in 2020.  Test or replace size 2032 CMOS battery before attempting reload.  Good batteries are good for 5 years.  If the battery is bad, which affects BIOS, reloading won't work.  I kind of wonder if we're dealing with that now.

@Dogs_Rule

You can try doing bcdedit /set {current} Description “TheNameYouWant”

Typically that will fix the error. 

Or yo can try 

​ bcdedit /set safeboot minimal

If those don't work run these first.

• bootrec /fixmbr
• bootrec /fixboot
• bootrec /scanos
• bootrec /rebuildbcd

Then re run the command for minimal boot.