Hi LuniLadi,
I understand that you are unable to install Windows updates on the computer because of AVG Internet Security. I do understand the inconvenience.
If AVG Internet Security is blocking the updates, I would suggest you to temporarily disable the security software and try to install the updates. Make sure to enable those security software's on the computer after checking. If disabling the security software resolves the issue then, please contact the specific security software manufacturer to resolve the issue.
Important Note: Antivirus software can help protect your computer against viruses and other security threats. In most cases, you shouldn't disable your antivirus software. If you have to temporarily disable it to install other software, you should re-enable it as soon as you're done. If you're connected to the Internet or a network while your antivirus software is disabled, your computer is vulnerable to attacks.
Hope this information is helpful and let me know if you need any further assistance.