A value from 1 to 25 that indicates the severity level of the error. The default is 0.
Remarks
Severity levels from 20 through 25 are considered fatal. If a fatal severity level is encountered, the client connection is terminated after receiving the message, and the error is logged in the error and application logs
Requirements
Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2