Service Packs are the means by which product updates are distributed. Service Packs can contain updates to improve system ...

Service Packs are the means by which product updates are distributed. Service 
Packs can contain updates to improve system reliability, program compatibility, 
security, and more. For more information on Microsoft Service Packs, see http://support.microsoft.com/default.aspx?scid=fh;EN-US;sp.