Lo and Behold.... I believe I have resolved my problem with the BIOS update that resulted in my husband's XPS 8900 boot loop. I'll update if there are issues later. No issues have been noted since I first posted this...
A Little Recap... Just our journey toward this solution. If you want to know what we did and how we did it, please look for my previous post ... skipped to solution...
Like someone else said, if you wish to try this, please do so at your own risk.
1. You must be able to get into Windows to try this fix. I was able to do this by booting to the OS CD that came with the computer, Dell Windows 7 Pro. It took several tries to get it to do this, but it finally came up. Repair and/or Restore, Reinstalling was not necessary for us. Restore wiped our programs, but not the files.
2. Microsoft uploaded a patch/update/fix (download below) that names this exact issue with this exact system. Download the file below, BUT DO NOT EXECUTE yet.
Microsoft File Fix: https://www.catalog.update.microsoft.com/Search.aspx?q=KB4078130
Read about the downloadable fix file above: https://support.microsoft.com/en-us/help/4078130/update-to-disable-mitigation-against-spectre-varian...
3. Download ALL Windows updates and install them. When all the updates are completely installed and the computer says it has to restart, DON'T!
4. After all the updates are installed, click the downloaded exe fix file from Microsoft (link above). Don't interrupt it.
5. It will say BIOS successfully updated if it worked. You should be able to successfully boot your computer to Windows now. If you don't get the message, check to see if you had any failed updates before turning the computer off. I originally tried the patch without updating Windows. Didn't know about a BIOS update message. I turned off the computer---back to the boot loop, so that's how I know about the updates first.
I sure hope this fix helps someone else out there. Please share if this works for you! Or even if it doesn't because then there is still an answer out there for you we just haven't found yet.
I was able to get into windows 7 after restore. I couldn't install all updates, some failed and some pending and restart should be done to complete updates. I tried to apply the file but didn't work. I downgraded the bios to 2.1.8 after chat with de agent, didn't work, also upgraded the bios to 2.1.10 and didn't work. I will restore again to get into windows. Any idea how to install all updates before restart?