I did a lot of research on Anti-Virus software, and was surprised to see NOD32 appear at the top of many comparisons. I had never heard of NOD32 or eset until I did my research, but with all of the positive reviews, I decided to install their 30-day trial.
NOD32 is excellent. It only uses about 25MB of RAM, yet handles a full suite of background scanning, including file system, network traffic, MS Office documents, and email. The right-click on-demand file scanner works almost instantaneously, and the virus signature files are not only updated automatically daily, they are frequently updated two or three times a day.
Some reviews mentioned that NOD32 has a clumsy user interface, though I found it to be clean and simple to use. But best of all, NOD32 has a very low impact on system performance, unlike McAfee or the other behemoth, Norton. What a relief to find a good Anti-Virus app.
Note: Like another one of my favorite apps, Servant Salamander, NOD32 appears to be developed in Eastern Europe. Is this the new home of fast, solid Windows software?