Why is my hard drive not found?

Check BIOS to see if the hard drive is detected, also check the settings for it. To get into BIOS or diagnostics, hit f10 when you see the Dell splash screen after restart. You can use diagnostics to test the drive if it is detected.

Things to try, remove and reinsert the hard drive. Try using an external drive case if one is available. Try booting with OS restore disk if available, the drive could be good but the boot files are corrupted. Replace the hard drive and install the OS and apps.

I have a dell inspiron 5748 that just did this. I reseated the drive, ran all the diagnostics, and the drive was clean. We then put the drive into a reader to see if it was dead. Nope worked just fine. It was the motherboard. I took the laptop apart(out of warranty) to see if there might be a loose cable and there was not a cable. the drive plugged directly into the board. So my suggestion is to remove the drive and have it tested. You can by a reader/repeater on Amazon for 20 bucks or see if a friend has one. If the drive is good then you know it's the board. I purchased an internal to external case for mine so it's now a back up external drive. I then parted the good parts of the laptop out and bought a new one.