For a free antimalware and antivirus app that also runs in your system's background, AntiVir works surprisingly well.
AntiVir's scans are flexible, allowing the user to fully scan all hard drives, choose a preloaded scan--for rootkits, for example--or customize a scan. Combining the antimalware with the antivirus is a luxury in a free scanner. After testing on several machines no viruses turned up, although several malicious hidden files did rear their heads. The heuristic scan can be turned on or off completely or partially, with three different intensity levels.
The quarantine is extensively thorough, too. The spreadsheet layout displays all relevant information about the quarantined file, and gives you options to scan it again, restore, delete, and more. The scheduler is fully customizable. However, the updater slowly chugs along, but thankfully updated definitions files are available at Avira's Web site. The help features in AntiVir were excellent, as well, with a description box relaying mouse-over information on each feature.
Initial concerns about the real-time Guard protection hamstringing system performance proved groundless. Although we could shut off AntiVir and its Guard, there was no way to remove the icon from the system tray or stop the occasional ad placement by Avira. The Complete Scan is numbingly slow, but it will stop midscan and let you know when it's found a threat. That's good for killing nasties, but it also means that you have to baby-sit it.
AntiVir's volume of features might take a while to get used to, but as long as the definitions file updates keep coming, this app's a keeper.