Helping people with computers... one answer at a time.
The concept seems simple: take a system image of one machine, restore it to another, and avoid lengthy setup time. Unfortunately, it's not that simple.
If I want to install a computer backup from a previous computer, complete with its operating system, onto another computer with a different operating system, will the operating system on the backup be allowed to install and override the operating system on the other computer? If so, how do I get around this?
It's not a question of allowing. By definition, restoring a full image backup will completely overwrite everything that exists on the hard disk, replacing whatever was there before.
So, sure, the previous operating system, along with everything else on the hard disk, will be overwritten and replaced with the contents of the image backup.
The real question is: will what you've just restored then work?
Most of time, the answer is a resounding no.
When you install an operating system such as Windows, the setup program goes
through what appears to be pretty much the same sequence of events that it does on every machine: you enter the product key, type in a little information, tell it what
machine name you want and perhaps the time zone, and pick an administrator password. Then, the setup goes to work, showing a progress bar or some
propagandainformation about the benefits of the operating
system you're installing and how wonderful your life together will be.
What happens behind the scenes is significantly more complex.
Almost every machine is different, and it's during Windows installation time that those differences are accounted for.
The Windows installation media contains software for hundreds if not thousands of different pieces of hardware that can be used with Windows. Only the software that applies to your specific machine is installed.
Windows Setup is as much a customization process as it is an installation process.
If your machine came with Windows pre-installed, this still holds true; it just all happened before you received your computer.
Let's start with a quick clarification. For purposes of this discussion, people tend to think of two types of backups: data and full.
A data backup is just that - a backup of your data and for the most part only your data. An example might be burning a copy of all your digital photographs to a couple of CDs for safekeeping.
A full backup also lives up to its name: it's a backup of everything. Typically creating what's called a "system image", this type of backup contains everything on the disk including not only your data, but your programs and Windows itself. A true system image can be restored to an empty hard disk on the same machine on which the backup was originally taken.
A full backup, then, contains your Windows installation, including all of the customizations that were made at setup time.
And that's where restoring to a different machine starts to fall apart.
If you take a backup image from machine A, and restore it to a different machine B it's extremely unlikely to work.
The problem is that all of those customizations that happened at setup time on machine A won't apply to machine B. The drivers installed for hardware on machine A that are not present on machine B will fail, and hardware that's present on machine B won't have the required drivers needed.
Given the incredible complexity of the hardware combinations possible with Windows, it's just not very likely that the scenario will work at all. Typically, the machine will simply and completely fail to boot at all.
It is possible for the scenario to work, but there are several conditions that must be met.
If those conditions are met, then maybe it'll work. And it's a huge if.
It's possible that Windows will be able to boot and that it may then notice that some non-critical hardware has "changed" and go through the process of updating itself, perhaps asking for driver or installation disks, and actually run.
It's actually a very common approach to installations that have a large number of identical machines, but the further you stray from truly identical machines, the lower your chances are of this approach working.
Just because you can't restore and boot from this backup image doesn't mean that the information in that image is lost.
One recovery method is actually quite simple:
Install Windows and whatever else you want from scratch onto your new or replacement machine (machine B, to use the terminology above).
Restore your backup image to a second hard drive that is not used for booting and access all of the data from there.
In fact, that last step is even optional. Many backup programs will allow you to browse and extract files from system images. You need not actually restore the entire image at all. Just find what you need and copying it out of the image.
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