An operating system wasn't found. Try disconnecting any drives that don't contain the operating syst

[WALUMAN]

An operating system wasn't found. Try disconnecting any drives that don't contain the operating system. Press Ctrl + Alt + Del To Restart 

[WAWood · Accepted solution]

@WALUMAN 

These problems are generally due to one of two basic problems:
1) Failed hard drive
2) Corrupted/missing boot loader files

As to the first, please follow the directions in this link for testing your hard drive: http://support.hp.com/us-en/document/c00439024

If that confirms your drive has failed, then you need to replace it. Please report back if that is the case.

As to the second, you will need access to a working PC for this step in order to create the media needed to repair your PC boot loader.

Once you have that, please download and create Win10 install media from this link: http://windows.microsoft.com/en-us/windows-10/media-creation-tool-install?ocid=ms_wol_win10

Yes ... I know that is for Win10, but it uses the same generation boot loader as Win8x, so it can be used to do boot loader repairs for Win8x as well as for Win10.

Boot from the media you created, and follow the directions in this link: http://www.windowswally.com/how-to-fix-error-code-0xc0000185/

You will probably have to run Startup Repair three times for it to fix all the boot loader problems.

When done, your PC should boot OK. If it does not, you have a more serious problem.

[TheOldMan]

While not the usual wording, that message indicates either there is a device without an operating system installed that is being addressed or the boot manager has become lost/corrupted.

Check for devices plugged into the USB ports or media cards in the card reader.  Of course, there is the possibility the hard drive has failed.

Sorry @WAWood   typing my response at the same time as you