This free, open source antivirus solution is essential for security-minded admins. ClamWin supports Microsoft Windows versions ranging from Windows 98 to Windows 8, as well as Windows Server 2012, 2008, and 2003. It includes a scanning scheduler that you can use to configure appropriate scan times, automatic signature updates, Microsoft Outlook attachment scan/removal, and more.
Although it may not be 100 percent comparable to a commercial real-time option for virus scanning, ClamWin is certainly a worthwhile tool, especially for shops seeking a free solution. There are other free solutions, obviously, but this one is also open source, a definite plus.