Service Pack 2, "SP2" for short, is Microsoft's most important release since XP itself. It aims to stop viruses, worms, browser hijackings and worse by including security features that people had to add and adjust on their own. (Users of Windows 2000, Millennium Edition, 98 and 95 will still need to do that, since Microsoft has no plans for a comparable update of those systems.)
The most important part of SP2 is an new firewall program to stop break-ins by network worms such as Blaster. Unlike XP's earlier firewall, this one is turned on automatically and protects every connection on a computer -- even if you already have another firewall active. It also watches what your programs do; if one wants to open its own channel of communication with the Internet, you'll need to approve this action.
Service Pack 2 is a free update, but it's not easy to get -- yet. A 266-megabyte download is available at Microsoft's site, while users with automatic updates enabled will have a smaller version sent to their PCs over the coming weeks. Around the end of the month, SP2 will be available on CD-ROM; to Microsoft's credit, it will ship these CDs at no charge. [Via]
If you run XP, you need to install SP2. Period.
