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Are there any known issues by installing an antivirus software or upgrading to (microsoft) service pack 2 or 3 ?
I have seen no issues running antivirus on the WCS server. If you want to be extra careful you can exclude the directory with solid.db in it:
Currently Windows 2003/SP2 and Windows 2003 R2/SP2 32-bit installations with all critical and security Windows updates installed is the supported OS specification.