Power off the computer. Disconnect all external drives such as external hard drives or optical drives and flash drives. I sometimes see that error because I have USB device set as higher priority in BIOS boot menu and sometimes I forget that I have an external backup drive connected. After disconnecting external drives, try to toot again. If it still doesn't boot, enter BIOS by repeatedly pressing F2 as soon as you press the power button. Ensure that your normal boot device (presumably an internal HD or SSD) is set as the first device in the boot menu. If it's not, edit that BIOS menu to move that drive to first priority. Try to boot again. If you still cannot boot, the drive should be checked for errors. Immediately after pressing the power button to turn on the laptop, press F12 repeatedly to enter the One Time Boot Menu, select Diagnostics and press Enter. The Dell Diagnostics will test all your hardware. If it finds errors, post them here. If Dell Diagnostics finds no errors, I would further test the drive. Sometimes a drive testing utility from the drive manufacturer can detect drive errors that more generic tools cannot. If you know the drive manufacturer, check their web site to see if they have a bootable utility that can be run from a flash drive or CD/DVD. Post back here for further instructions. If all hardware testing finds no errors, then it may be a problem with the Windows installation or boot files. Do you have a Windows Recovery USB flash drive? Did you create one for this system? If yes, insert it into a USB port on your laptop. Immediately after pressing the power button to turn on the laptop, press F12 repeatedly to enter the One Time Boot Menu. Choose to boot from the USB flash drive containing Windows Recovery. There are various tools there that may repair the boot files on your drive to enable you to boot normally. If you're at this stage, post here and I can give you more instructions.
No bootable device found? What is your go-to fix? For more questions regarding this contests, please visit the Contest Information Page here.
DS 07/20: No bootable device found? What is your go-to fix?