Topic: What is the lightest "Free" or cheap AV application out there?

[FPF-DieHard]

Currently using the free Security suite from Optonline for home use.   it's not bad but I have to snooze the virus protection before gaming otherwise I get stuttering.   

[FRA.E.Kehakoul_XC]

I use this, its exellent.

A-squared Anti-Malware 3.5 Free

http://www.emsisoft.com/en/software/free/

Download page.

http://www.emsisoft.com/en/software/download/

[Bonk]

I've been using ClamAV. The secret is no resident on-access scanner - on demand only. All of a sudden your computer is yours again. Scan only when you want and it has a full command line interface for scripted scans.

There are several flavours for windows:

Clamwin

ClamWin is a Free Antivirus program for Microsoft Windows 98/Me/2000/XP/2003 and Vista.
ClamWin Free Antivirus comes with an easy installer and open source code. You may download and use it absolutely free of charge. It features:
    * High detection rates for viruses and spyware;
    * Scanning Scheduler;
    * Automatic downloads of regularly updated Virus Database.
    * Standalone virus scanner and right-click menu integration to Microsoft Windows Explorer;
    * Addin to Microsoft Outlook to remove virus-infected attachments automatically.

ClamAV Antivirus Native Win32 Port

Unofficial native port of the well known ClamAV Antivirus, this port is used in ClamWin Antivirus

and the "official":
ClamAV for Windows

From here you can download a version of ClamAV for Windows. Previously only available for UNIX-like systems, the release of  ClamAV on the Windows platform marks a breakthrough in AV technology for Windows. This version is native, that is it was built using Microsoft's Visual Studio 2005 and requires no emulation layer such as Cygwin.

...

Please note that ClamAV is NOT a desktop AV system, it is aimed to the server market.

The latter two are not for the inexperienced user, it takes considerable configuration and tweaking. I'm using the one at http://oss.netfarm.it/clamav/ becasue it has the daemon and its maintainer keeps pace with official engine releases.