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The chances of SP2 crashing your machine is low, but here are a few precautions to take before installing that will help you avoid a potential crash.
Will SP2 Crash my machine?
There's been a lot of press about Windows XP SP2 crashing or hanging machines or applications. The good news is that like most "news", you only hear the bad stuff. In fact, the news reflects only a minority of installations - the vast majority of SP2 installations are working great. The bad news is that if you're in that minority, it doesn't matter to you that it works fine everywhere else.
So what can you do to make sure that you stand the highest chance of success?
Here are a few steps to take prior to installing SP2:
Make sure you have room: The process of installing SP2 can take up to 1.8 gigabytes on your hard disk. That's not how much room it will take up once installed. SP2 doesn't take up nearly that much room once you're done installing. However the process of installing, including making backup files, setting a restore point, copying temporary files around, and so on may require that much room on your primary hard drive.
Check the release notes, and known problems list: Microsoft had made a ton of information available for Windows XP Service Pack 2, and I've included links to important documents and portals below. Two of the most interesting to review prior to installation are Release notes for Windows XP Service Pack 2, and Some programs seem to stop working after you install Windows XP Service Pack 2. The later, in particular, includes a list of applications that are known to have issues with Service Pack 2. In many cases, updates or workaround are already available from the various manufacturers.
Read Microsoft's "Before you Install" Article: What to Know Before You Download and Install Windows XP Service Pack 2 is an overview article that Microsoft has provided that covers several of the topics I've covered and several more. In particular it includes links to step-by-step instructions for actually installing SP2.
At this writing, Windows XP Service Pack 2 has been out in the field long enough that I feel confident enough to endorse installing it. The vast majority of SP2 installations have gone smoothly and without incidents. A lot of the noise about problems is due to a small percentage of applications that were behaving improperly to begin with, or security related changes that simply require user intervention before being allowed to continue.
I run SP2 on my computers running Windows XP, and have had no issues.