The Dell diagnostics say that the hard drive has likely failed.
Dell will repair this under warranty.
BUT - If it's a dying hard drive, the first thing to do is to attempt to recover your data. Because it's dying, you may only have a limited time to recovery it (so now isn't the time to experiment with it - as each time you access the drive it'll tend to shorten it's remaining lifespan)
The easiest way to do this is to boot from a bootable disk to recover the data that way, or to "slave" your hard drive to another computer and see if you can copy the "Users" folder
1) Copy it to the Documents folder so it doesn't get itself confused with the Users folder on the working computer
2) Make sure that you set the working computer to view system and hidden files (this'll let you capture the AppData folder which may have bookmarks and email)
3) Make sure that the working computer has plenty of space, as the User folder is usually quite large.
There are different levels of data recovery.
Should you choose to take this to a pro, here's what it may cost:
- Level 1 (what I described above) $100 to $250 (US)
- Level 2 (using recovery software) about $500 (US)
- Level 3 (taking the disk apart and putting the platters into a new drive) $1700 to $2000 or more (US)
Once that's done, let Dell fix it under the warranty.
You can do it yourself, but you'll need a new hard drive and the recovery media (and the skills to open up the system and replace the hard drive).
Good luck!
