XPS 8700, need help after removing BIOS battery

Generally speaking, when you remove the BIOS battery, you have a certain amount of time to replace it before the system forgets its BIOS settings.  Turning it ON with the battery removed probably did not help this.  Turning it OFF possibly upset the OS boot.  It might be a mess.

With the original memory and a battery installed (everything like it used to be), I would try to boot into the BIOS and inspect the settings to see if it all makes sense.  If by chance it's still configured as it was, I would exit without saving anything and let the OS do its thing.  If the OS boot offers options, try to proceed with a normal start.  Trying to reset or do something special may only makes things worse.  If the BIOS seems to have lost its settings, then you may need to stop and do your homework before moving forward to recover your system

Know that you can always rebuild the system with your desired memory and a new/better system disk, and then install your existing storage to recover your data.  This may be a better course of action than trying to recover your OS disk and corrupting your data.  Unfortunately, I have no experience with Win10 builds.

Keep notes and consider each step as the right next step to make.  Flailing forward can make matters worse.  Remember... "do no harm".

GK

Were you mistakenly following instructions for replacing memory on a laptop instead of a desktop? Never remove the bios battery when doing any repairs or upgrades. It's laptop batteries that have to be removed since they provide power when the laptops are unplugged. The bios battery remembers the bios settings when the computer is not attached to power outlet.

See if any of this helps-- https://www.dell.com/support/article/en-us/sln300716/how-to-recover-the-bios-on-a-dell-computer-or-tablet?lang=en

@RunXPSRun You do not need to recover the BIOS. The BIOS should be OK since you did not try to update the BIOS. What you need to do is return to a valid set of BIOS settings. I recommend that you start by following the procedure in the Owner's Manual for Clearing CMOS Settings which should return the settings to their defaults. I also recommend that you go back to a known working configuration by removing the new RAM you were trying to install. Usually changing or losing your BIOS settings should have warranted an automatic repair of your OS that requires resetting your PC. The one exception to that last statement may be the SATA Mode setting (either RAID or ATA). If you don't know what the original setting was you may have to try one and then the other. Dell recently delivers systems set to RAID, not sure what they used for the XPS 8700.

Thanks for the quick replies-especially given all that's going on right now with coronavirus.

It seems to have fixed itself after I disconnected the SATA cables from all the hard drives.  The only drive connected to the MB was the SSD drive with the system already installed. 

So here's what I was experiencing in case this happens to anyone else - at startup the Automatic Repair kicked in which took me immediately to the blue diagnostic/repair page.  Selecting "Continue" just restarted the PC and put me back in the same place.  Selecting the Troubleshooting options didn't help either.  Under Troubleshooting if I tried to reset the PC under any of the options - e.g. keeping or deleting the files - I would get the same message that the PC could not be repaired.  Going into the BIOS and trying to reset everything by selecting defaults didn't help either.  I finally gave up (this was before I had gotten the suggestions above) and decided to reinstall the OS from a startup disk I created a few years ago.  Unfortunately, the OS installer refused to install the OS in any of the hard disk partitions. (I may need to create a new system startup disk).   I got an error message at each drive and partition I tried to install on.

A friend of mine who was spitballing with me at that point suggested I remove all the SATA cables from the hard drives to isolate the SDD and try installing it again there.  I was probably an hour into the troubleshooting at that point.  So I removed the SATA cables from the hard drives, started the PC up expecting it to boot off the startup disk as it had before.  But this time it started normally and my desktop popped up as normal.  At that point, I connected each HD one by one and restarted each time.  

All back to normal.  I'm guessing after resetting the BIOS it was selecting the wrong drive to boot up from but I'm pretty sure the boot order in the BIOS was set correctly even after I reset to default settings.