Inspiron 3671 BIOS update failed

The error message is obvious.  Since you can't update within Windows, just put the BIOS image file on a USB drive and run it from F12, one time boot menu.  Here is the instructions:

Updating the BIOS from BIOS Boot Menu (independent of operating system)

Note 1: Before updating the BIOS, ensure that you suspend BitLocker encryption on a BitLocker-enabled system. If BitLocker is not enabled on your system, you can ignore this step. For information about how to disable BitLocker, see How to Enable or Disable BitLocker with TPM in Windows at support.dell.com.
Note 2: Do not turn off the power or interrupt the BIOS update process during the update.
Note 3: Your system requires a restart after installing the BIOS. The restart can be deferred but must be completed to ensure that the update is installed.

Installation
1. Copy the downloaded file to a USB drive. You do not need a bootable USB drive.
2. Insert the USB drive into any USB port.
3. Power on the system.
4. At the DELL logo screen, press F12 to access the one-time boot menu.
5. Select BIOS Flash Update in the Other Options section.
6. Click the ... button to browse the USB drive to locate the downloaded file.
7. Select the file and click OK.
8. Verify the existing system BIOS information and the BIOS update information.
9. Click Begin Flash Update.
10. Review the Warning message and click Yes to proceed with the update.
The system restarts and displays a Flash Progress bar at the Dell logo screen. The system restarts again when the Flash update is complete.

@kevinInspiron3671  - You probably don't need to do a BIOS update to install Win11. But, if you really want to update BIOS, at least use the latest version, 1.21.0, not the old version, 1.10.0, that you linked. Do this update while Win 7 is still running and confirm everything works correctly after the BIOS update, before going further.

If you don't update BIOS, or after the new BIOS is installed/working, open BIOS setup (reboot and tap F2) and make sure these settings are correct.  If necessary, change them in the order listed:

Legacy Option ROMs: Disabled (enabled by default)

Secure Boot: Always Except Internal HDD (default setting)

PTT: Enabled (disabled by default) (This PC model uses PTT (software) instead of TPM (hardware).

Unless they're all set correctly, Win 11 won't install. And the first two have to set as indicated or you may not see the option to enable PTT in BIOS.  Be sure to save the changes before exiting BIOS setup. PC will boot Win 7 automatically, and again, make sure everything is working. 

Now back up all your personal files on an external drive. Don't bother with software files because you'll have to install all apps in Win 11. Just make sure you have the Product Keys for your apps so you can activate them in Win 11.  If you don't have them, run Belarc Advisor (free) in Win 7 to find them and print out the results because all that info will be lost when you clean install Win 11.

Use the Microsoft Media Creation Tool for Win 11 to prepare a bootable USB.

Right before you start the clean install of Win 11, go back into in BIOS setup, and change SATA Operation to AHCI, because it's probably set to RAID.

WARNING: PC won't be able to boot Win 7 after you change SATA Operation to AHCI, so be certain you have everything you need from the boot drive backed up before making this change. 

Might be a good idea to image the entire boot drive before you change SATA Operation, while Win 7 is still running, just in case. You can use software like Macrium Reflect (free for 30 days) to create an image of the entire boot drive, and save it on an external drive. And use Macrium's option to create a bootable USB, if you need to revert back to Win 7.

@Chino de Oro​ Thanks.

At BIOS update step 5, I couldn't find the "other" options. My BIOS version is old (A05).

<Private data removed from public view. DELL-Admin>

Verify that your USB drive is formatted FAT32, and non-bootable.

Download and save this BIOS image file to your USB drive  Vostro_3471_3671_Inspiron_3471_3671_1.21.0.exe

Boot your PC and immediately tapping F12 until you see the message for one time boot appears.  Then select the BIOS flash update again.

You also have to plug that USB stick into PC with power fully off. Then power on and tap F12. Otherwise, it won't see the USB drive or the file on it.

And the USB has to be no larger than 8 GB.

Upgrade to Windows 10 first, as Windows 11 is only a free upgrade from Windows 10. Check your activation status afterwards. If it's activated, then upgrade to Windows 11 (continue below). If not, Windows 10 was not previously installed and activated (before October 2023) or the BIOS does not have a Windows 10 key etched in. In either case of Windows 10 or 11, you will need to purchase a license in order to activate Windows and to use all of its features. I suggest you put that money towards a new system instead.

If Windows 10 activation is successful, download the Windows 11 ISO image from Microsoft's website. Use a free program called Rufus to copy the ISO image to an empty USB flash drive that's 8 gigabytes or more in capacity. Upon creating the image to USB, a dialog box will ask you to customize the image. Here you should see an option to disable the TPM 2.0 and secure boot requirement. Check that and continue. This will allow you to "unofficially" install Windows 11 on systems that don't meet the TPM 2.0 or secure boot requirement. Once the image has been copied over to the USB flash drive, install Windows 11 from it.

Note, Windows 11 is 64 bit only. Since you are upgrading from a 32 bit architecture, you will need to perform a clean install of Windows, which will erase all personal files and apps from the system. Please backup any files before you continue installing Windows.

Note:  Microsoft did away with free upgrade from Win7 to 10.

@bradthetechnut​ That's why I mentioned before Oct 2023. Any system that was upgraded for free from 7 or 8.1 to 10 and successfully activated before that date will still activate upon a clean reinstall of Windows 10. Since then, new upgrades from 7 & 8.1 to 10 that were never activated will no longer activate, and will now require the purchase a Windows 10 or 11 license.

This is pretty much Microsoft's attempt to push sales of new Windows 11 systems and to get people off of older ones, much like their TPM 2.0 requirement that many older systems lack. I'm surprised the Windows 10 free upgrade program lasted as long as it did, even though it was suppose to be available for 1 year from the initial release of 10 in 2015.

"That's why I mentioned before Oct 2023. Any system that was upgraded for free from 7 or 8.1 to 10 and successfully activated before that date will still activate upon a clean reinstall of Windows 10."  Sorry, missed your exact wording somehow.