Tiburon Homes, LLC has managed to avoid viruses such as Conficker and Vundo by using the free ClamAV software on their computers that run Windows XP.  ClamwinAV, the Windows version of the ClamAV, is a free and open source software package that has often rated higher than propriety products such as Symantec and McAfee.  Using a combination of ClamAV and Firefox, Tibuon has been able to keep their IT security high while keeping their costs low.