I removed the CMOS battery for 15 minutes, depressed the power button for 15 seconds then replaced the battery and turned it back on.  It continues to do the same. The power button remains lit white seems like it's going to boot, then shuts off, then turns back on, then same thing off again, then back on and so forth.

What a terrible shame this is.  I have so much work to do.  So much hope for this. 

Is there anything that can be done or is this thing toast??  Unf*nbelievable.

What you did should have cleared the CMOS, but you may want to try the procedure on page 84 of the owner's manual: https://downloads.dell.com/manuals/all-products/esuprt_desktop/esuprt_xps_desktop/xps-8700_owner%27s%20manual_en-us.pdf

Also you may want to test the CMOS battery or get a new one.

Ok, I will try that this evening.  Help me understand, by clearing the CMOS settings, will that reset the installed BIOS down to a default version?  

Thanks for your time.

** Update, I googled it ;)  yep it's what I thought.  I will try tonight and report back.  Fingers crossed 

Clearing the CMOS will reset the BIOS settings to their default settings. Clearing the CMOS will not change the BIOS version, so if you have installed A13 successfully it will remain A13.

1. I cleared the CMOS settings by moving the jumper to position 1:2 then waited 30 seconds then back to position 2:3

2. I replaced the CMOS battery with a new one.  The computer still does the same. Reboots on its own, never see anything on the screen. Over and over again.

I am gutted.  Is this the end of the road?  Does anyone have any more suggestions?

Because your problem started immediately after a BIOS update, I am afraid I can't get pass the thought that the BIOS was corrupted by that update attempt. If that is the case, there is no recovery from that short of replacing the motherboard. Perhaps someone else has some other thoughts or suggestions.

I am not one to cause many waves and complain, but I feel in this case although my computer is out of warranty- Dell should replace my motherboard: all I did is follow the instructions to a T on what to do and how. For Dell's BIOS software to have fried my motherboard is in no way my fault.  My computer was running like a dream before this incident. 

Newer machines have Dell BIOS Recovery 2/3 Procedures possible.

https://www.dell.com/support/article/us/en/04/sln300716/bios-recovery-options-on-a-dell-pc-or-tablet?lang=en

You are not the first.

Here is Dell Policy:

https://www.dell.com/community/Customer-Care-Wiki/Dell-Policy-BIOS-update-breaks-motherboard-CMOS/ta-p/6063959

Here is a better (safer) way to flash your BIOS (including instructions if it has UEFI ability/Environment)

https://www.dell.com/community/Vostro-Desktops/Vostro-460-XPS-8300-Upgrade-Adventures/m-p/6071757/highlight/true#M1311

I just called Dell out of warranty support (800-288-4410) and explained word for word what happened.

"The computer is out of warranty and you must pay $39 to have it shipped to our service center, then we'll call you and tell you what is wrong and how much you need to spend to fix it"

Awesome.

thanks for the info, hard lesson learned.

Does anyone know around how much it costs to have a motherboard replaced by Dell ?