Microsoft releases service packs for many of their products containing Windows and Office. These service packs generally are out to address many problems with product in regards to bugs, security and various improvements in product. Before release these updates separately, Microsoft places them all into one update known as service pack.

in Service Pack 3 change the behavior of Office 2003, containing changes that stop some aspects by default and raise control for PC administrators. This service pack also contains fixes that have been before released as individual updates for Office 2003 like Service Pack 1 and 2 so you do not want to install these initially.