Microsoft Office Compatibility Pack Service Pack 2 (SP2) gives customers the latest updates to the Office Compatibility Pack for the Microsoft Office Word 2007 Open XML file format, for the Microsoft Office Excel 2007 Open XML file format, and for the Microsoft Office PowerPoint 2007 Open XML file format.

This service pack includes two main categories of fixes: 

•  Previously unreleased fixes that were made specifically for this service pack.
  Note In addition to general product fixes, these include improvements in stability, in performance, and in security.
• All the public updates, security updates, cumulative updates, and hotfixes that were released through February 2009.

http://support.microsoft.com/kb/953331