By the time this message appears, the machine has started up and passed self-tests and is now at firmware level. Only the final step failed. Boot files take up a few hundred megabytes of space; everything else that actually matters is somewhere else on the disk, not affected.
About half of the time all is well with the disk (something about where the firmware was told to look has changed). The other half it is failing, and the BIOS will typically tell you which.
When this message appears, the machine's firmware has scanned for something to start from but found nothing familiar. The drive may be perfectly healthy: what failed could have been the boot configuration, the partition table, the boot order in the BIOS or the connection to the drive.
There are really two separate problems when most folks think of them as one. Will your computer start and will we get access to your files? They are very distinct issues with the second usually being much easier to resolve than the first.
Does your data mean more to you than the ability to use the computer? Then do not begin by attempting repairs. Any repair attempt (startup repair, rebuilding the boot record, reinstalling) will result in writing to the hard drive.
Is the drive listed in BIOS? If yes, then it is not hardware but either your boot configuration or partition layout. If no, then it is either hardware related or connection related.
Has anything changed? Firmware updates, adding a new drive, resetting the BIOS or switching from Legacy to UEFI all cause this issue without there being any fault.
Is it making noise? Grinding or clicking alongside this warning message indicates mechanical failure of the drive. Shut down immediately instead of trying again.
Do you need the machine or the data? If it is the latter, then please stop here, remove the drive from the system and do not attempt to repair it. Any repairs will write to the disk and may make the recovery process more difficult.
Only if you're willing to take that chance with your data. That writes out to disk (and on a failing drive, that write can frequently fail).
It could be hardware, it could be the connections or firmware. First check by trying a different cable and port. If you get no sound from a mechanical drive then most likely the fault is with the board.
Often this is due to an error in either the partition table or boot record as opposed to the actual failure of the drive. Most likely all of your data will still be intact underneath.
A single drive will cost from £300 +VAT and we will commit to it in writing after the free diagnostic.