HI depending on what av product your friend has on her computer it is always a good Idea to be on the safe side to uninstall the first av product and then install the second av the reason being is that when you disable some av’s they still run in the background on your computer to stop viruses and malware from disabling your av so that it can function to remove the malware from your system. If you install a 2 av on your computer the second av that has resident protection could cause your computer to crash and make it very unstable. In short uninstall the first antivirus completely then do a clean install of the second antivirus witch is avast free. Then if your friend does not like avast for some reason. Then uninstall avast free from the computer and install your previous antivirus product back on the computer.

This may seem like a lot of work and bother but it is better to do the above then have the computer become unstable and then you will have to take it to a repair shop to get it fixed right.

have a good weekend