Why does installing from scratch take so long? Isn't there a better way?

As we know by now, all software has bugs (there are no exceptions) and over time, more and more bugs are discovered and fixed. Once fixed, however, we run into a dilemma: how to get the fixed software into the hands of the people using older versions.

The traditional approach is to release a new version - the new version completely replacing the old. This is the approach most often used by applications as version X.000 gets replaced by X.001, then X.002 and so on. I know many of the applications I use get updated rather frequently as issues are resolved and even as new features are added. Through various means, typically online update checks, you're notified and the new version is downloaded and installed automatically.

The key is that it's a complete replacement of the application, even for minor updates.

That works well for small to medium sized applications (though the definition for "small to medium sized" seems to be growing over time).

That approach doesn't work well for large applications (like, say, Microsoft Office), or operating systems like Windows (or Mac OSX, or Linux). While some people think nothing of downloading an entire CD's worth of data (~700 megabytes), or even a DVD's worth (usually up to 4.7 gigabytes) it's simply still not practical for most people.

The approach taken is to create individual updates for individual components - typically downloading and replacing only smaller pieces of the whole.

Naturally, the process of downloading only things that have changed reduces the amount of downloading required. Even better are those systems, such as that used by most operating systems, that download only what's changed only for those components you actually have installed. If you're not using something there's no point in downloading an update that you also won't use.

The whole process is designed to minimize what you need to download.

Unfortunately, over time the amount you need to download only increases as more and more bugs are found and fixed and occasional new features added.

If you're installing using an original Windows XP disk as it was first released, an installation today has to download nearly 10 years of updates. That's going to take a while.

Microsoft has tried to mitigate the impact of that a several ways:

• Service Packs: Service packs bundle a number of fixes into a single package that is then installed at once, reducing the number of individual downloads, optimizing the installation process, and presumably reducing the number of reboots.

• Service Packs on Disc: Service packs themselves tend to be rather large, so Microsoft typically makes them available on CD as well, or as separate monolithic downloads that can be downloaded once and applied to several computers offline.

• Service Packs Pre-installed: After releasing a service pack, Microsoft typically refreshes the product disks that it sells, incorporating the service pack contents into the actual product image. You'll often see things like "Windows XP w/ SP2" on the box. Subsequent installs are instantly up to date as of that service pack. (You can also perform this process, called "Slip Streaming", to create a "Windows XP w/ SP2" image from your vanilla XP CD and the monolithic SP2 download.)

• Critical Fixes: by categorizing updates as critical or not, Windows Update automatically gives you only those fixes you need - typically security related updates - and allows you to pick and choose the optional updates you may or may not be interested in.

• New Products: The only update of Windows that really encompasses the entire operating system is, of course, a completely new version. Windows Vista and Windows 7 both represent completely new versions of Windows, and reset the incremental update process.

The bottom line is that there's really no way around the fact that taking a reinstall from scratch - particularly from older original install media - and getting it up-to-date is going to take some time downloading and installing the updates that have been released since that install CD was created.

There is one way to side-step it, though. Particularly if what you have is an older XP installation CD - say, perhaps, prior to SP2.

• Install Windows from your original installation media.

• Get it as up-to-date as you can.

• Now, take a complete image backup of the system.

That image backup can serve as a "snapshot" of your updated system. Save it, and in the future you can use your backup program to restore to that already-updated image rather than installing completely from scratch. The results are the same, and it saves you all that updating time on subsequent reinstalls.

It doesn't help the first time, before you have that snapshot - you still have to get Windows up to date the traditional way. However, if you then ever have to reinstall Windows again, you'll have this image and can avoid going through the pain to get to that point again.