Ok. First can you check if you have a windows defender service running by going to start, and search for services. Second check your registry for this key: H_KEY_LOCAL_MACHINE/System/CurrentControlSet/services/WinDefend. In the WinDefend folder there should be 3 subfolders labeled parameters, security and triggerinfo. Let me know if you have the windefend service running or these keys in your registry.
You don't have a "CurrentControlSet" subfolder? It should be listed right below the two you named. If not try this anyhow just be sure to back up your registry before hand. After backing up merge this with your registry and reboot. Report any changes.
Attachment 158601
I know this is an old thread, but I just wanted to say a BIG THANK YOU to phw8558.
My Windows Update Service was not working on my PC (for a few months(12)
from a virus I got - what-I've been busy
- spent ages (when I could) trying to get it going, but to no avail. 
So, I eventually/reluctantly set aside 2 days to do a full rebuild
but though I would have a final dig around.
Found a separate thread on SevenForums that pointed to Windows Defender (WD). (never realised it could be WD)
Checked mine - not on, and getting error "The specified service does not exist as an installed service. (Error Code: 0x80070424)." when I tried to switch it on. (I was running McAfee, which I realise may have switched it off, but even after I uninstalled it, I was still getting the same error).
Then came across this thread. I was a bit dubious about downloading the file, and then merging with my registry, but though I had nothing to lose!
==============================================================
So, here's what I done.
1. Created a System Restore Point - (
Create a restore point)
NOTE! - This will overwrite any previous system restores (automatically created weekly)
2. Stopped Windows Update Service (may not have made a difference, but wanted to have a complete clean slate - again, wasn't working anyway - and it will restart on reboot) [Start>Control Panel>Administrative Tools>Services - or Services.msc from search]
3. Uninstalled McAfee - (
How to uninstall or reinstall supported McAfee products using the Consumer Products Removal tool (MCPR))
4. Restarted PC (a couple of times)
5. Ran Malwarebytes Anti-Malware (available
Malwarebytes : Free anti-malware download)
6. Opened Regedit & backed it up (type regedit in windows search, open it, then File>Export)
7. Downloaded windefend.reg from phw8558 post (thank you :) phw8558 )
8. Merge registry (On Regedit again, File>Import, select downloaded windefend & save/open)
9. Restart PC
10. Start Windows Defender (from Control Panel)
11. Click 'Check for updates now'
12. Once WD is complete, windows Update service starts automatically :):):)
13. Once it's all up and running, Restart PC
14. I would also suggest running a last 'Malwarebytes Anti-Malware' to confirm all clear.
15. You can then reinstall you McAfee, or use MSE (
Microsoft Security Essentials - Microsoft Windows)
==============================================================
Anyway - hope that helps someone in the same predicament.
Thanks again to all who post here and other forums. For us amateurs, you're lifesavers 
Michael