Desn't recognize Harddrive

Provided that the hard disk is properly seated (check the connections), then your hard disk is most likely failing.

Once you get it to boot again, back up your critical data.

Then call Dell service and see if it is under warranty. You are going to have to replace it, one way or another.

I have a user that something like your problem.
He left it a his car overnight. He travel the next day for about 2 hours, then when inside to teach a class. He laptop keep failing to start.
He called me and told me about his problem.
I asked him if the laptop is warmed up? He said why!
I told him in the winter it can take several hours for the laptop to warm up after being in a car at 10 degree F. The moisure it the laptop can damage his motherboard when it is cold. You would not run water over it would you and turn it on before drying it out.
After a couple hours he called back to say that his laptop was okay and work great again.

Winter weather and laptops can be problems.

Keep laptops insde at night helps stops problems like this.

I hope this helps
Good Luck

I suspect ol' BFilm is probably correct. Sounds like the on-board drive electronics are starting to fail and BIOS can't recognize drive because info is not being provided by drive.

This is definitely the time to back up before it quits completely.

Dalton