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The SMS_Executive service process (Smsexec.exe) consumes high CPU resource on a Microsoft System Center Configuration Manager 2007 Service Pack 1 (SP1) site server. The CPU usage on the CPU can be up to 100%. This problem occurs when Management Information Format (MIF) files are processed. Therefore, this always occurs after a new site is installed and can occur after the SMS_DEF.MOF file or the Configuration.MOF file is changed.
Read the complete post at http://wmug.co.uk/blogs/cliffs_blog/archive/2009/09/22/ms-kbs-high-cpu-usage-during-mif-file-processing-on-system-center-configuration-manager-2007-sp1-site-servers.aspx