ESET's SmartSecurity 3.0 is by far the best antivirus, firewall, anti-spam, anti-malware, internet security suite I have ever tried. First of all, the software doesn't take much of your system resources so you could expect your other programs to run fast. I've been using it for several months now and my computer has not been infiltrated ever since. Unlike with other anti virus and firewall software I've tried before, which either got me several viruses and malware enterring my system, or would cause my computer to hang.
I find ESET preferable to Avast, AVG, Norton, and McAfee, not only based on experience, but based on statistics and reviews I've scoured from reliable sources on the internet. I could find several antivirus programs claiming to be better than others, but I haven't found one that could claim to better than ESET.
If you want top level protection for your computer, then ESET SmartSecurity is definitely the best choice. ESET provides a free 30 day trial, which I suggest you take. You'll be convinced at the power of ESET.