Computer running slow and intermittant internet problem at Kenilworth in Warwickshire

Good morning we are with a customer on Windy Arbour at Kenilworth in Warwickshire, we are here because the customer has reported that their computer is running very slowly, its found that the phone line has a noise quality issue which will effect the internet connection quality and will cause our intermittent internet problem, we investigate further and find that we also have a second issue slowing down the computer, that is the computer has 2 antivirus programs installed and they are conflicting with each other, after removing one and editing the registry, and checking all up to date this computer was working at a good speed again.