Companies often release a service pack when the number of individual patches to a given program reaches a certain (arbitrary) limit, or the software release has shown to be stabilized with a limited number of remaining issues based on users' feedback and bug tracking such as bugzilla.
For example, Windows XP SP3 contains all the fixes that are included in Windows XP Service Pack 2 (SP2).
Office XP, Office 2003, Office 2007, Office 2010 and Office 2013 service packs have been cumulative.
Depending on the operating system and deployment methods, it may then be necessary to manually reinstall the service pack after each such change to the software.
This was, for example, necessary for Windows NT service packs; however, from Windows 2000 onwards, Microsoft redirected setup programs to use updated service pack files instead of files from original installation media in order to prevent manual reinstalls.
Con's: Many users have complained about complicated installation glitches when it comes to the XP Service Pack 3 and have warned that people should download with caution.
Internet Explorer 7 is also not included in this package.
Installing a service pack is easier and less error-prone than installing many individual patches, even more so when updating multiple computers over a network, where service packs are common.
Service packs are usually numbered, and thus shortly referred to as SP1, SP2, SP3 etc.
My issue was with Windows Zero Configuration Service after install of SP3.
Just had to restart the service manually from control panel and BOOM, internet works.
The rgscvr32 has to be run to enable the Windows update on the system.