Windows 7 Home Premium laptop spontaneously reboots after login following recent Windows Updates

My personal laptop is having an issue.  It’s an ancient Dell Vostro 1500 running Windows 7 Home Premium x86.  After some recent Windows update, the laptop will spontaneously reboot after logon.  (If left at the logon screen, it will stay there indefinitely.)

I have traced the issue to the CNG Key Isolator service—if that service is disabled, the laptop will not spontaneously reboot, but it also will not have any network connectivity.

There is no minidump file, and the settings are enabled so that Windows should create one.

If I do an in-place upgrade (basically a Windows repair), the laptop will boot and run normally with all services enabled, but as soon as it hits whatever Windows update (out of the ~180 that are needed), it goes back to spontaneously rebooting.  (I have tried the offline WSUS updater and it runs in the same issue.)

If booted in Safe Mode with Networking, the CNG Key Isolator service starts and runs, and the laptop has network connectivity and does not reboot.  

From what I understand, the CNG Key Isolator service is calling to some file or service that is having a problem, but I am not having any luck figuring out what.  The Event Log is pretty much worthless.  This laptop has multiple specialized pieces of software on it that are either hard to come by or difficult to reconfigure, so a format and reinstall is not an option.
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SINC_dmackAsked:
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JohnBusiness Consultant (Owner)Commented:
Start in Safe Mode and see if it stays running.

Look through MSCONFIG and see if you can remove items from Start Up and see what the issue is.

Here is information on CNG Isolation. It could be a key logger.

http://www.blackviper.com/windows-services/cng-key-isolation/
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SINC_dmackAuthor Commented:
As mentioned, the laptop has network connectivity and does not spontaneously reboot if booted in Safe Mode with Networking.  

I have used MSCONFIG to disable startup programs and services--that's how I determined that it is the CNG Key Isolation service that's causing (or at least tied to) the spontaneous reboots.

I am confident that it is not a keylogger and that the laptop is not infected.
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SquigglyMonkeyCommented:
In safe-mode look through the scheduled tasks for any 'at logon' scripts and check them.
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JohnBusiness Consultant (Owner)Commented:
The article says "The CNG key isolation service is hosted in the LSA process" so maybe if you stop the LSA process temporarily
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SINC_dmackAuthor Commented:
I handed off my laptop to one of my techs and he threw the whole barrage of the Tweaking.com Windows Repair Tool at it.  Apparently something in there fixed it, because after he gave it back to me, it was fully updated and didn't have the issue any more.

http://www.tweaking.com/content/page/windows_repair_all_in_one.html
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SINC_dmackAuthor Commented:
I handed off my laptop to one of my techs and he threw the whole barrage of the Tweaking.com Windows Repair Tool at it.  Apparently something in there fixed it, because after he gave it back to me, it was fully updated and didn't have the issue any more.

http://www.tweaking.com/content/page/windows_repair_all_in_one.html
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