An operating system wasn't found  

NavyLCDR said:

Just to confirm, @pxfragonard, your initial problem has been fixed?

I suppose so. Thanks. But some things are really screwed up. I couldn't make a bootable USB from this machine though I could from the laptop. And there are some warnings.

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zbook said:

What happened between posts #16 and #28?

That's a concerning question! But I did finally manage to create a bootable flash drive on the laptop (the desktop wouldn't even recognize it in diskpart) and managed to put the diagnostics from HP on it too (though, again, I wasn't able to from the desktop).

I'll post them as soon as I can. A number of things seem to have been reset but yes, some things that passed now fail.

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Matthew Wai said:

The step takes less than 20 seconds. "DiskParInfo.bat" will get information about storage devices.

There is no need to say "sorry". You are not the first one and will definitely not be the last one.
Jut run the following script and upload "Tuneup.log" from the desktop.
Tuneup_plus_log

It's posted in #28. I apologized for not being able to get the text box to work although it did. It just wasn't visible in "preview this post." I just apologized to be polite and to express the knowledge that Paul was spending time on my behalf, that I appreciate it, and don't want to cause him more work.

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zbook said:

What happened between posts #16 and #28?

I finally got a bootable usb made but when I pressed F2 I didn't get what was expected. The option to run overnight wasn't there. I investigated and this is all I found. Now, although things are working, something seems odd. For example, in System Information, it now says I have UEFI when I know my BIOS is legacy. Wondering if I should press F10 again and set it to default. Anyway. I hope these photos show where I went looking for the program you suggested using.