Hello Paul,
I regret for the inconvenience caused.
Please let me know the error message you receive when you try to install AVG Ultimate.
You can also send us the screenshot http://avgclick.me/getscreenshot, we will check the same and assist you further.
Paul, For your info, just in case that you are unaware, you can post the screenshot here in your topic. Click on 'Answer' & then click on the 'Image' [mountain symbol] & follow the instructions.
AVG Guru