Hi Marc,
I'd have to agree with @Tony Sutton at this point. If you have the option to do so, backing up your data and then having this system wiped and rebuilt would be your best bet, and would help to ensure that you have a good security posture moving forward.
I noticed there is nothing even showing up as being installed from Symantec or Norton. So whatever is blocking your Windows Updates is just some leftover remnant at this point - possibly in the registry.
I think your best two options would be:
- Ideally, backup your data and wipe the laptop, then re-install Windows
- If the above option won't work, try a manual removal as @Brian suggested earlier, but this could be tricky based on what we've seen so far
I really hope this works out okay for you. Please post again and let us know how you decide to proceed.