Inspiron 15 3520

The error stating that a drive couldn’t be found during a Windows 10 installation on a system already running Windows 11 can be due to several reasons.

Here are some steps you can take to troubleshoot and resolve the issue:

Check BIOS Settings: Ensure that the BIOS is set to the correct boot mode. If your system is UEFI-based, you should be using a UEFI bootable USB for Windows 10 installation.

Disable Fast Startup: Windows 11’s Fast Startup feature might be preventing the installer from recognizing the drive. Disable Fast Startup in Windows 11 before attempting to install Windows 10.

Check the Partition Format: The partition you created for Windows 10 should be formatted with the NTFS file system and marked as ‘Active’. You can use the Disk Management tool in Windows 11 to check and format the partition.

Load Storage Drivers: During the Windows 10 installation process, you might need to load storage drivers, especially if you have an NVMe SSD. You can usually download these drivers from the laptop manufacturer’s website.

Change SATA Operation Mode: If your laptop’s BIOS has an option for SATA Operation (such as AHCI or RAID), changing this setting might help. However, be cautious as changing this setting could affect the existing Windows 11 installation.

Create a New Bootable Media: If the bootable USB drive you’re using for the Windows 10 installation is not recognized, try creating a new one using the Media Creation Tool from Microsoft. DogNearMe

Secure Boot: If Secure Boot is enabled, it might prevent the installation of another operating system. You can try disabling Secure Boot in the BIOS settings.

Remember to back up any important data before making changes to your system.

In case you don't find the AI response useful, the usual cause is a drive that's running in IRST (Intel RAID) mode.  For that, you need to pause the installation with F6 where indicated and load the driver you'll find here:

https://www.intel.com/content/www/us/en/support/articles/000091139/technologies/intel-rapid-storage-technology-intel-rst.html