Ive been using Avast Antivirus on my home PC for more than a year now. After using Avast, Ive not yet found a reason to shift to another antivirus package. Here are the key features which prompt me to stay on with Avast :
Easy & Fast Updates: You can configure Avast to automatically update its Virus Database every time you connect to the net. Unlike other Antivirus updates, which are huge and take ages to download, Avasts updates are quite small, and update in a flash. This is a huge advantage if you are a dial-up user.
Tiny footprint: Unlike Norton or other commercial antivirus packages, Avast is quite compact and doesnt eat up into your system resources. The every new version of Norton seems to slow down systems more and more. The English version of avast is around 8.10 MB when you download it.
P2P Shield : When youre using a P2P network to download files, Avast can scan the incoming files to make sure that youre not downloading viruses with the files. (This feature works on when you are using avast on Windows NT/2000/XP/2003)
Free for Personal Use : You can use Avast free of charge if you are a Home or non-commercial user. Youll need to register youself as a home user and get your free License Key. (https://avast.com/eng/free_virus_protectio.html) Since I installed this on my computer, Ive hardly had to worry about viruses on my machine. Ive got my friends to install Avast on their machines, and now all of them are hooked on Avast.
You can download Avast Home Edition from: https://avast.com/eng/down_home.html