Good KB article from Microsoft about configuring anti-virus software on windows
http://support.microsoft.com/kb/822158
This article contains recommendations that may help an administrator determine the cause of potential instability on a computer that is running a supported version of Microsoft Windows when it is used with antivirus software in an Active Directory domain environment or in a managed business environment.
Note We recommend that you temporarily apply these procedures to evaluate a system. If your system performance or stability is improved by the recommendations that are made in this article, contact your antivirus software vendor for instructions or for an updated version of the antivirus software.