Alwil Software's Avast 4 Professional Edition came in with a disappointing sixth-place finish in "Virus Stoppers," our eight-program antivirus roundup, despite a decent 92 percent success rate at detecting malware (compared to 96 percent for top performers).

Its ranking was hurt by its poor performance in our proactive tests: Avast caught only 37 percent of new malware using one-month-old signature files, the second-worst showing. For disinfection, its performance was about average. It cleaned all infected files, but missed changes to the Hosts network settings file and some less-important Registry entries, catching 78 percent of all possible items.

The program installed smoothly, with appropriate default settings for the average person. It offers two interface options: One is a distinct, media player-type control panel that makes it easy to figure out how to launch a scan or set a manual boot-time scan; a second "enhanced interface" lets you access and fine-tune more settings, but it's not nearly as user-friendly as the other option.

After installation, Avast runs one full-system startup scan. But in the awkward advanced interface, we could not find a place to set up a regularly scheduled scan. The only option we could find enables scans whenever the screen saver is running, but even this setting was difficult to locate. And Alwil Software does not offer phone support in the United States.

Avast scans a good range of e-mail and news protocols, including POP3, SMTP, IMAP, and NNTP. It also scans all Web traffic. And Avast's comprehensive instant messaging protection fully supports several popular IM clients--AIM, ICQ, MSN, Skype, Trillian, and Yahoo Messenger--as well as lesser-known chat tools such as Gaim, Miranda, and Pal Talk Messenger.

Avast maintains a useful, built-in Virus Recovery Database on your PC, which you can theoretically use to repair infected program (.exe) files. (We didn't test this functionality.)

This paid Professional version costs $40, with a $28 yearly renewal fee. Alwil Software also offers a free Home version, which lacks some features such as the ability to run scheduled scans and view previous scan results.

We tested the Vista version of Avast 4 Professional Edition for our "Virus Stoppers" roundup. An XP version of the software is also available.

-- Ryan Naraine