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Today, April 12, is the day. Like it or lump it, Microsoft is pushing Service Pack 2 to your XP machines even as you’re reading this.

If your customers have Automatic Update turned on, ready or not, here it comes.

Now for many of you, this is going to be just another day. You’ll probably be more concerned with Microsoft’s other patches which are scheduled to come out today.

But, then again, there are going to be some of you—OK, a lot of you—who are going to be having fits today as your customers call in to report application after application breaking down.

By the way, Microsoft, come on! A major patch Tuesday and making SP2 downloads mandatory on the same day? Are you really sure your servers are up to this? And what makes you think IT staffers will be up to the challenge?

You see, AssetMetrix, a service provider that also analyzes IT infrastructure, recently found that about 38 percent of business PCs are now running XP, and of those only 24 percent were running SP2.

Let me do the math for you: about 27 percent of your customers’ PCs may be acting goofy on Tuesday.

Oh boy.

So, what can you do when your phone starts ringing?

First, Don’t Panic!

Most of the problems you’ll be seeing will not be real incompatibility problems. They’ll be problems with applications running headlong into XP SP2’s Windows Firewall.

The short-term fix is just to turn the firewall off. That defeats its purpose, of course, but at least the applications will be running again. You can spend Tuesday evening reactivating the firewall so it can do its job while letting the appropriate programs do theirs.

For a full description on how to go about doing that, see this Microsoft Knowledgebase article.

At the bottom of that same article, you’ll also find a list of known applications that have issues with SP2. For many of them, like Symantec AntiVirus Corporate Edition 8.0, the fix is simply a matter of opening up the right network ports.

Don’t think, by the way, that just because you run nothing but Microsoft software you’re safe. Microsoft programs, like SQL 2000a and Microsoft Systems Management Server 2003, can break under SP2 if the firewall settings aren’t right.

I really hope that you don’t have spyware on your systems. Bad, bad things can happen when spyware that’s already resident tangles with SP2. If your systems are having real fits after SP2 lands, run several recently updated anti-spyware programs—no single one catches all of them—to try to clean them out. Then reboot.

Now, if one of your homegrown applications, especially one that relies on Internet Explorer, starts breaking…Well, let me just give it to you straight. Unless it’s a firewall problem, you may be hosed.

It took months and several attempts for one company I know of to finally track down and eradicate an application-killing bug that kept wrecking its content management system.

There are programs that can help your developers find these bugs. I’ve heard strong recommendations for Identify Software’s software-execution logging programs for this kind of job. But, come on, if you have to go that far, you’re well beyond a quick fix and into a serious development effort.

So what can you do if your customers are stuck with a non-working vital application? Well, you’re going to need to roll back the operating system to XP SP1.

The best way that I know of to do this is to use Winternals’ Recovery Manager 2.0.

If you haven’t been using it, you can always do it the old-fashioned way and use the Add/Remove Software applet from the XP control panel to rip SP2 out by its roots.

However, I’ve run into trouble from time to time with this approach. What I usually see is multiple programs giving me “Entry Point Not Found” errors. Endlessly.

What’s happening is that XP SP2 was only partly uninstalled, so the system is dealing with a mishmash of SP2 and SP1 files. It’s not pretty.

While I haven’t been able to find a Microsoft knowledgebase article that deals with this particular problem, the method described for how to get rid of that kind of error in one particular case has also worked for me with the more general problem.

It’s for that reason I prefer Winternals. Or, of course, you could always just restore the workstation’s operating system from its backup. Uh, you do have a backup, right?

After getting rid of SP2 by hook or crook, you simply make darn sure that SP2 isn’t installed on the problem systems until you finally have your application troubles ironed out.

Don’t think, though, that you can put off SP2 forever. You can’t. Microsoft is putting its security efforts into XP SP2, not SP1, not Windows 2000; XP SP2 is the Windows desktop moving forward.

And, besides, while it’s not perfect—I counted 16 post-SP2 fixes on an XP machine I upgraded on Sunday—it’s still a lot more secure than any other Windows system out there today. It just often isn’t that easy to install in the first place.

Good luck.