I ran a Windows 10 update and my Desktop will not boot up.

Hello Ron,

Thank you for your reply. Other friends suggested the F keys. I did get the F12 to provide a list and I am running what I think is the correct thing- Diagnostic? I am not an IT literate person and have never had a computer malfunction like this so bear with me. I may have further questions if the 'testing' it is performing does not clear up the problem. 

Others have suggested I ditch Windows. Should I and what would be a recommended operating system?

For What It's Worth (and no one here will agree with me) running Windows Update automatically is a recipe for disaster.  I run Windows 7 and 8.1 and pick and choose updates that I feel are useful (about 5% of what MS offers) and ignore the rest.  I have been through what you are going through one too many times.  As for PC security, I have my own firewall, antimalware, and antivirus, I do not need or want Microsoft's security toys.  #politicallyIncorrect

Hopefully, you have set restore points, and will be able to access them via Windows 10 Recovery.  Once, when I was not able to access my restore points after a Windows Update disaster in Windows 7, a neosmart.net recovery CD located the restore points and saved me, so that's something to consider as a very last resort (they're $20).  

Users do not have the option to "OPT OUT" of windows updates in windows 10.

In previous Windows versions, we could choose what updates are downloaded and installed. In Windows 10, users have almost no control over updates. You can choose only how updates are installed, but you cannot turn off or disable Windows Update in Windows 10 from the control panel.  If you disable the service windows defender never updates leaving the machine vunerable to malware.

I ran the F-12 option with no positive result other than the scan option says everything 'works' on this particular computer.  BTW- It's a Dell 620 built on 11-21-11.  So it looks like I will have to re-install an operating program to regain function of this machine.  Disappointing, but I very much appreciate the help.  My assumption is that Windows 10 caused the problem.  I will look for other options for this Dell.

Try the repair first.  If you do a full reinstall, you'll lose all your files, if they're not backed up elsewhere.

If files are not backed up, you could remove the hard drive and install it as secondary drive in another PC to rescue your files, but another PC won't boot from this drive. Or you could use an external SATA>USB cable to access the files on that drive.

I presume you mean Optiplex 620.  Keep in mind that Dell doesn't support Win 10 on this system, so it's possible the latest Win 10 update just isn't compatible with your hardware. Of course, it could just have been a failed update...

BTW: No Win 10 support from Dell if this is an Inspiron 620, rather than an Optiplex 620...

For What It's Worth (and no one here will agree with me) running Windows Update automatically is a recipe for disaster.

Good to know, thank you. I'll delay my update to Windows 10 even longer. :)