Service packs are the means by which Microsoft distributes bug fixes. Service packs keep a product current. Service packs include updates and may include system administration tools, drivers, and additional components, which are bundled for easy downloading.
Service packs are cumulative; each new service pack contains all the fixes that exist in previous service packs, as well as any new fixes. You do not need to install a previous service pack before you install the latest one.
Service packs are cumulative; each new service pack contains all the fixes that exist in previous service packs, as well as any new fixes. You do not need to install a previous service pack before you install the latest one.