VM won't boot, says "Windows could not complete the installation" yet this is a long running vm

[dgingeri]

I have a customer Windows Server 2016 VM that refuses to boot, saying "Windows could not complete the installation" on boot, and the only option is to reboot, which brings up the same thing.  It seems guest os customization is malfunctioning, but I cannot find enough info on it to find where the files are it is using to impose the guest os customization or get the OS to bypass it.  

I have tried everything in the gui, with absolutely no change.  I can hit shift-f10 and get a command prompt, but I can't find anything to tell me what's going on to figure out how to bypass the guest os customization.

I just found the bootexecute setting in the registry (I hadn't run into that setting in 20 years of Windows support) and altered that, still no good.  

In short, how the frick do I get this stupid VM to STOP trying to run the guest OS customization??

BTW, I do NOT want to sysprep or rebuild this VM.  It has been running successfully for over 6 months, and our customer has done a lot of work on it.  They have 70 people employed by their customer using it, at least 30 on a daily basis.  

[dgingeri]

Well, it has to be something with the guest os customization settings in the VM config as well as something in the OS, as a restore from backup of the C: drive didn't fix it.  We had to do a full VM restore from backup and then attach the old drive to the restored VM to get data.  This is a pretty nasty glitch that needs to have a fix, possibly some sort of tool to check the VM settings in vCloud Director and correct errors, like a file system check on a storage drive does.