XPS 8930, not opening Windows 10

if you have the original Dell Windows 10 installation DVD, put it in pc and boot from it, and go into advanced to do a system restore back to original factory configuration.  If you do not have DVD, make a Windows 10 installation media usb by download from Microsoft official site.  Either way boot from installation media DVD or usb then do system restore.

PS Windows 10 password is not the same as admin password in BIOS.

@cferguson56 Since your PC has been unplugged so long you may wish to replace the coin-cell battery on the motherboard. 

Thanks, I don't seem to be having any trouble with the battery.

Also, Dell did not provide a CD for Win10 with the machine and that is why I attempted using the USB option.

I created the Dell USB boot file using the Dell instructions, but the computer does not see the USB drive at the start of the boot up and does not run the file from the USB flash drive at startup. It appears to be stuck in a loop that is attempting to update Win10. The Win10 "Updates" screen appears for a millisecond, showing 64% completion of the update, but then exits that screen and begins the boot up cycle all over again (this is the screen that only shows "Dell" in a circle).

I wouldn't be surprised at all if the motherboard battery does need replacing, as @Vic384 already said, because the PC was unplugged for almost a year, and was totally dependent on that battery to hold the correct BIOS settings, which it may not have done.

You could also try to force Windows into its recovery environment:
Power on and when you see the Dell splash screen, immediately force power PC off by pressing/holding the power button on PC. Immediately power on and then off again. Repeat the on/off cycles 3 times and it should boot to the recovery environment where you can troubleshoot the booting issue.

Re: It appears to be stuck in a loop that is attempting to update Win10.

your pc is booting 1st from hdd that has the broken Win10.  You need to press F12 immediately after power up and keep pressing until you see a boot device order, then use up/down arrow to choose usb device.  Make sure usb flash drive is plugged in before you attempt this.

I will try the 3 times method, thanks.

I successfully created a USB Win10 file using instructions provided on the Microsoft Technical Support webpage. I then have used the F12 screen to access the Win10 options such as “Repair Your Computer”, “Reinstall Window”, “Reset Win10 to a restore point”, etc. I have tried all the options and the issue is not resolved, it is still performing the Dell boot cycle (indicated by the word “Dell” in a circle logo) then starting Win10 with a screen that shows “Updating Windows, 64% complete, do not turn off your computer”, then aborting and cycling through the same process. And It continues to do this over and over again.

@cferguson56 , if all else fails, performing a clean install may get your computer working again.  Go to Microsoft website and download the tool to create Windows 10 installation media (USB).  

• Tap F12 and select booting from the Windows installation USB
• Select to install windows, not upgrade.  Select custom mode to view and delete all partitions on existing drive.  No need to format, windows installation will perform this step prior to installation.
• To set up as local account, unplug your ethernet and select I don't have internet, you will see option to enter new name and password.  Else, enter your Microsoft account and set up this computer as one of your devices.
• When installation complete, connecting to internet will allow new windows 10 to be activated base on your hardware ID.
• Go to Dell website to download and update your chipset, intel management engine interface driver.
• Restart your machine, go to settings and run update to get remaining drivers, some drivers are hidden under optional update.

Chino,

@cferguson56  That sounds like it's hung up installing an update, possibly because Fast Startup is enabled inside Win 10.

But unless/until you replace the motherboard battery, you're shooting in the dark, and risking having to wipe your drive and reinstall...

The battery is only ~$2 so even if it doesn't solve the problem, you've at least ruled it out and haven't spent a lot of money doing it...

Re:  risking having to wipe your drive and reinstall...

@RoHe , Op forgot the password to get in Windows.  Beside replacing the coin cell battery, wiping the drive and reinstall seems like the final option.