Many readers are likely familiar with the fact that Windows 7 comes with a fairly comprehensive backup solution that includes, among other things, the ability to create a so-called system image of your entire PC. This system image is, more precisely, an exact duplicate of the hard drive(s) in your PC, in VHD (virtual hard disk) format, and it provides you with the ability to fully restore your PC to a previous, known-good state.

Pedantic sidebar: By default, the system image capability in Windows 7 only backs up "the drives required for Windows to run." The exact nature of these "drives" varies from system to system, and understanding how it works is even more confusing because of the way Windows 7 automatically partitions a hard drive. On a single disk system (most PCs and virtually all laptops), this will be the first (and only) fixed disk (i.e. "hard drive"), which is segregated into a hidden reserved partition and what we think of as the C: "drive" (which is in fact a partition, not a drive, but whatever). In the olden days, the C: drive would typically include the functionality of both the "startup disk" (the disk/partition that contains the files required for booting the PC) and the "system disk" (the disk/partition that contains the WINDOWS directory). And in Windows 7, that's pretty much how it works, though it's still possible for the startup and system disks to be different disks or partitions.

What this means to Windows Backup is that the system image capability will typically backup the C: drive only. But if you have partitioned the disk differently, or are dual-booting among two or more OSes, it's possible that it could include two or more partitions (or drives). If your configuration is more complicated than that, you can also use Windows Backup to manually create system images for the other disks and partitions in your PC.

The system image capability in Windows Backup is good at what it does. But it has other uses beyond the obvious. And one of those uses is an increasingly common scenario: You've got a PC with whatever hard drive in it, and it's running out of space. If you have a desktop PC, you might be able to simply add a new hard drive. But if you have a laptop, you almost certainly can't. In either case, however, there are advantages to not adding a hard drive but instead replacing the existing hard drive with one that offers more capacity and, perhaps, better performance.

The trick, of course, is doing so without losing anything: Your data, your installed applications, your settings, and so on.

I used Windows Backup for just this purpose recently. I've been using the same ThinkPad SL410 laptop for about a year now, and while it has the best keyboard I've ever used, the stock 320 GB hard drive isn't particularly voluminous and I was wondering whether I could get better performance out of a more modern hard drive. So I purchased a Seagate Momentus XT "hybrid" hard drive, which combines a small amount (4 GB) of solid-state storage with 32 MB of cache and a 7200 RPM hard disk to create a package that offers much of the performance of a true SSD drive for a fraction of the cost. Indeed, the 500 GB version I purchased cost just $109 on Amazon when I purchased it (though I notice its $129 today for some reason).

Here's how to make the swap.

For purposes of this exercise, I'm going to assume you're doing this with a single disk system like the laptop I used. You will need a USB hard disk or other supported backup media (which includes recordable DVD discs and, with Windows 7 Professional and higher, a network share) and a blank, writeable CD (or DVD).

First, manually create a system image of your PC's hard drive. You do this via the Backup and Restore control panel, which is the front-end UI for Windows Backup in Windows 7. There are about a hundred ways to reach this window, but the simplest, perhaps, is to open the Start Menu, type backup in Start Menu Search and tap Enter. You should see something like the following shot.

Click the linked titled "Create a system image" in the task pane to start the wizard. It will search for an acceptable backup device, and, if found, present it in the "Where do you want to save the backup?" phase of the wizard. Otherwise, you can manually point the wizard at an acceptable backup point.

Click Next and the wizard will show you where it's backing up to and what it's backing up. On a single disk system like the typical laptop, this will again be hidden, reserved partition (System Reserved) and the C: drive (System).

Click Start Backup to create the system image. This will take some number of hours, depending on the used disk space, your PC's overall performance, and the performance characteristics of the backup media. I backed up to a USB hard drive and it took several hours.

When the system image is done, the wizard will prompt you to make a System Repair disc. I recommend doing so, though you can launch this process separately from the main Backup and Restore interface later if you'd like.

A system repair disk is a bootable Windows 7 CD (or DVD) that provides two capabilities: It can present the various Windows 7 recovery options or use a system image backup to restore your PC to a previous state. You'll be using the latter functionality.

Once the system repair disc is done, eject the disk and shutdown the PC.

Now, unplug everything (cables, power supply, laptop battery, whatever) from the PC and remove the current hard drive. How you do this will of course vary from PC to PC, but on the ThinkPad it involved removing a panel on the bottom of the machine, sliding out the hard drive in its protective cage, removing the cage from the old hard drive, and then attaching it to the new hard drive. Then, insert the new hard drive, put everything back together, and reboot the computer, re-inserting the system repair disc so that the PC boots from that. (If the hard drive you've installed is truly new, the PC won't boot otherwise, anyway.)

When the system repair disc boots up, you'll be presented with a screen in which you choose between the recovery tools--which can be used to solve problems with your current Windows OS--or to "restore your computer using a system image you created earlier. Obviously, you want the latter option.

The Re-image your computer wizard will attempt to find a suitable system image file located on a device attached to the PC. If it can find one, it will present that as an option automatically. Otherwise, you may need to manually select the correct system image.

After that, you're given the opportunity to exclude certain disks, which applies to the target PC and not the imaged disks you're restoring. This can be useful in certain conditions, but for the single disk restore we're doing here it's not worth worrying about.

Then, you can click Finish to start the restore process.

Oddly, the restore process takes considerably less time than the backup. In my case, I believe it completed in under an hour. When the process is complete, the PC will reboot into the exact same Windows install--complete with all your custom settings, data files, applications, and whatnot--as before.

There is one final task, assuming the new disk is larger than the old: Windows Backup will restore the contents of the old C: drive to a new C: drive that is the same size as the old one. So you'll need to use Windows 7's disk partitioning tools to expand this partition to use all the extra space. Curiously, this tool is pretty well hidden, but you can find it by typing partition in Start Menu Search. You will see a control panel calledCreate and format hard disk partitions appear in the search results. Click that and the Disk Management tool appears.

Looking at Disk 0, you'll see some empty space after the C: partition. To use this space, right-click the C: partition (and not the empty space) and choose Extend Volume. Then, in the window that appears, tap Enter as needed to add all that empty space to the C: partition. When you're done, the C: partition will have been resized to be larger.

A few notes

One of the nice things about this process is that it's non-destructive. If something goes wrong, you can always get your old system back by putting the old hard drive back in the PC. In fact, you might consider saving that disk as-is as an in-time backup of sorts.

One of the other nice things about this process is that replacing a hard drive is not typically enough to trigger Windows Product Activation. So you won't need to worry about re-activating and, potentially failing an electronic activation attempt that would force you to call Microsoft, hat in hand, and ask for their eternal forgiveness. (OK, it's not that bad.)

Finally, this process also obviates the need to fully account for all of the provisioned applications and services on your PC. I'm talking about things like iTunes Store, Audible, and Zune Pass, which have only a certain number of associated PCs; this process will not waste a PC "slot" with these services. But it's also true of activation-protected software, like Microsoft Office and Adobe Acrobat. You won't have any issues with these or similar software titles.