Run Windows 7 on your XP or Vista PC

Windows 7, Microsoft's new operating system, makes many improvements over Windows Vista, and still more over XP, but it's common to feel a little nervous when switching to a brand-new operating system.

For starters, it's possible that older hardware won't work until new drivers have been released and, besides, it always takes time to feel fully comfortable with a new working environment.

If you haven't investigated Windows 7 yet, take a look at Computeractive's feature outlining 10 reasons you should upgrade to Windows 7 and our review of Windows 7.

It's possible to try out Windows 7 while keeping an existing Vista or XP installation in place. By creating a 'dual-boot' computer, you'll be able to choose which operating system to use each time the PC is switched on. Using a technique called partitioning you can split an existing hard disk up and create an area specifically for Windows 7. We explain how.

Be prepared
Before you start, make sure you have the Windows 7 installation disc at the ready. The existing hard disk will also need to have plenty of free space for a practical Windows 7 partition - 25GB should be enough. We also strongly recommend backing up all your important data.

Although partitioning hard disks is safe when conducted carefully, it is possible to accidentally select the wrong option and lose photos, documents and other file types. It's better to be safe than sorry.

Partition primer
Before we explain how to install a second operating system, it's important to understand the basics of hard-disk partitioning.

If, for example, a new 500GB hard disk is fitted to a PC it will show up as a single 500GB drive. Partitioning is the process of splitting up a single drives such as this into multiple 'logical' drives.

Of course, on the outside the hard disk will remain a 500GB model, but once partitioned Windows will see it as two or more individual drives. Each partition will have its own drive letter and they will all be treated as completely separate disks.

There are many advantages to partitioning a hard disk. Imagine, for example, three partitions on a single disk: one for all the Windows files, another for installed applications and the third for personal data, such as documents, photos, music and video files. Should Windows ever need to be re-installed, the other two partitions can remain safe and untouched.

When it comes to installing two or more operating systems on a single PC, partitioning is essential since each operating system will need to be installed on its own drive (be it a physical drive or a logical partition).

Create a new drive
In this Masterclass we'll be installing Windows 7 on a PC that is already running Vista. If you're running Windows XP, the process isn't as straightforward as XP doesn't include the necessary tools to 'shrink' an existing hard disk (we'll talk more about shrinking in a moment).

For more help partitioning XP drives see Partitioning in Windows XP later. In Vista, though, it's a relatively painless process.

First, log in to Vista using an administrator account. Now click the Start button and then right-click Computer. From the list of options, select Manage.

After a short wait, the Computer Management window will appear. Look at the list on the left side of the window and click on the Disk Management option. Vista will now gather information about all the hard disks installed in the PC.

When it has finished, take a look at the graphical list of drives located in the bottom section of the window. All installed drives (including CD/DVD drives) should be displayed here. It also displays how many partitions each drive has.

Many computers come with hard disks that have already been partitioned. One of the partitions may relatively small and home to a set of backup files that can be used to restore the computer to its original state: this is known as a recovery partition, and it will have been put there by the PC manufacturer.

To create a new partition on a hard disk, 'unallocated space' is required. To create some on an existing hard disk, one of the existing partitions will need to be shrunk.

Right-click on the one labelled 'C:' (it may also have a name next to it) and then select the Shrink Volume option.

After a short wait, a new window will appear. The first entry tells you how big the existing partition is, while the second tells you how much it can be shrunk by. The third box is where you specify how much of that space you want to shrink it by, while the fourth indicates how big the existing partition will be after you've made the changes.