No Operating System Found

This is my first time on here so I hope I am in the right location for the problem I have.

I have a Dell XPS 8300 with i7-2600 CPU @3.4 ghz.  It came with Windows 7 but upgraded to Windows 10 before I seen a Dell post saying not to upgrade the XPS to Windows 10 so I am not sure if the error I am getting has anything to do with it.  It worked fine till about a month ago.

I have never had any problems with my PC till I plugged in a friends U-drive to help him with a resume. I was using Word 2013 when it froze, then my PC froze so I did a hard reboot. Everything came up as normal but I couldn't find the word document I was working on. MS Support said to do an all files search using   .wbk files   and to click on the file and search for the missing word document. I did that and a program started loading called    adware.bp . I click don't install and conducted a search again for the word document and the same program popped and started loading again. I again clicked don't install and then all my problems started.  

I found the document and I started working on it. I closed Word and came back to it and it said Word was not initialized. I clicked on Excel and it said Excel was not initialized. I did a normal reboot and I got the error ' No operating System Found ', I did a complete Dell Diagnostic check and everything came back as normal operating condition. Both hard drives are working, ram is working and everything else checked out fine. I accessed the BIOS and everything is showing up on there. I ran an Ubuntu program and all files and programs etc are fine and all partitions are in place. Everything seems normal but my PC won't boot up at power on.

My recovery disc doesn't work and I have tried Windows 10 recovery and that didn't work either.  I was going to do a factory rest but the F8 key doesn't work as well. I thought a virus must have loaded from my friend u-drive so a ran a bootable virus program and the first thing it said was my PC was in sleep mode and to wake it up. I have no idea how to do that with the issues going on with my desktop PC.. 

I have downloaded all the files and photos I want to keep. Now I would like to do a hard factory reset if that is possible. I've been told to do a Windows 10 re-install but I will loose all the partitions which I don't want to do if at all possible.  

I'm sorry if I have been a little long winded but I don't know how else to explain what is going on with my XPS 8300. If anyone is familiar with what is happening on my desktop,  I would really appreciate the help or advise in getting it running again.