(FORTUNE Magazine) – When Star Trek's Captain Jean-Luc Picard ventures into hostile territory, does he wait for aliens to pound the Enterprise with plasma torpedoes and then patch it up with Galactic Fix-It Goo? Hell, no! He orders, "Shields up!" and the torpedoes bounce off harmlessly.

When you connect your Windows-based personal computer to the Internet, do you wait for the Slammers, the Welchias, the MSBlasters, and the Sassers to bore through your operating system's well-publicized security holes? Do you then patch the holes with globs of Gates Goo?

Of course you do! That's the way things have worked in the world of Windows. But in August Microsoft will release new software called Windows XP Service Pack 2, or SP2, an update to the world's most popular PC operating system.

Normally I don't write about prerelease (beta) software, because no good can come from loading untested and potentially damaging software on your PC. It may look appealing, but the results can be unpleasant, much like eating from street vendors in Mexico City. The perils increase if the beta program modifies the operating system, the core software that controls all aspects of your computer.

But I can't boot up my Microsoft Windows computer without wondering, every day, whether some hacker has found another Windows vulnerability to exploit--has someone turned my PC into a spam-spewing zombie? Have I picked up a virus that is giving my corporate network the digital version of las turistas? Is someone in Idaho stealing my identity? So I decided to download a prerelease version of Windows XP SP2 from Microsoft.com.

Unless you're proficient with bits and bytes, you should wait until Microsoft formally releases Windows XP SP2 as a free upgrade in mid-August. But don't wait a day longer. The new service-pack software replaces the old patch-the-holes system--the Gates Goo patch system--with proactive "Shields up!" security features that will immediately make Internet computing safer and less annoying for Windows users. The upgrade will be free, and the benefits for most PC users will be significant.

Windows service packs don't normally add new features to the operating system; typically they fix problems or improve compatibility with third-party applications and hardware. This time, though, the problems with Windows security had become so great that SP2 was sent back to dry dock for some armor plating. SP2 adds layers of protection between your PC and your Internet or local network connections. It hardens the machine against attacks, known as buffer overruns, on the memory system. It girds the Internet Explorer browser to make it less vulnerable to tricksters ranging from pop-up advertisements to fake websites. And it toughens the e-mail and instant-messaging programs to reduce spam, viruses, worms, and other crud known as malware. On top of that, SP2 adds a new control-panel item called Security Center that makes it easier for the average PC user to check and manage the security status of his PC. There's also a new wizard, or guided tutorial, to help simplify the process of setting up a secure wireless network.

Windows XP SP2 comes just in time. Constant bombardments of viruses, worms, Trojans, port probes, spam, spyware, and other digital threats make some Windows PC users want to flee to the relative safety and security of Apple's Mac OS or Linux or some other operating system. But for the vast majority of PC users, switching operating systems and equipment is not a practical option.

That's why Windows XP SP2 is important. Right out of the box--or to be precise, straight from the server--the upgrade fixes some of the egregious flaws in earlier versions of Windows. For instance, the default settings assume you don't want strangers poking around in your files. Previously Windows came from the factory with its firewall protection system disabled and file-sharing ports wide open.

SP2 starts out by urging the user to activate a long-available (but seldom used) application called Automatic Updates, which enables the PC to check in regularly with Microsoft HQ for the newest security updates and patches. The way it worked before, Microsoft would post a notice on its website essentially saying, "Attention: We have discovered a secret trapdoor that could allow aliens to sneak into the ship, but you can download this patch to fix the problem." The trouble is, the aliens can download the patch, reverse-engineer it, and devise a torpedo to exploit the known vulnerability before most users ever see the original warning. And the aliens are getting really good at it: It took hackers 331 days to exploit a security patch with a bomb called Nimda worm, 180 days to exploit a patch with SQL Slammer, 151 days for Welchia, 26 days for Blaster, and just 17 days for the most recent one, Sasser. The trend is not encouraging. With Automatic Updates, the user gives permission to the computer to check with Microsoft and automatically install patches before the wily aliens can get in the door.

The problem, of course, is that rational users may be wary of allowing Microsoft, a certified predatory monopolist, to sniff around inside their machines for unique hardware information, version, and validation numbers for all Microsoft software, Internet IP addresses, and so on. To help assuage such paranoia among customers, the opening installation screen of SP2 boldly notes, "No information is collected that can be used to identify you or contact you." But moments later, when SP2 triggered an automatic error report after installation, a second notice appeared: "... the error report may contain customer-specific information in the collected data files. While this information could potentially be used to determine your identity, if present it will not be used." Why can't I shake the image of Bill Gates as the alien Borg telling Earthlings, "Resistance is futile"?

Much of what SP2 does is protect users from their own laziness or recklessness. Despite years of warnings that one should never open e-mail attachments from strangers, at least one doofus in every home or office will open a strange attachment. SP2 quarantines attachments in an isolation tank until they can be proved safe or until the user overrides it.

If Microsoft deserves credit for improving the security and user experience of Windows XP through Service Pack 2, it also deserves opprobrium for not doing a better job with Windows security in the first place. (It's sort of like giving credit to Ford for fixing the problem with exploding Pintos.) Even so, Windows XP SP2 is boldly going where Microsoft has not gone before, and that's good news. Shields up, and thumbs too.

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