Run Windows 7 on your XP or Vista PC

Choose the disk size
Windows 7 requires at least 16GB of disk space, but it's best to provide plenty of room, because it will expand as time goes on. As a minimum, we recommend at least a 25GB partition for a Windows 7 installation. When choosing the size, bear in mind how much space to leave free on the existing partition;
Windows won't allow all the available space to be used, but you'll want to make sure there's enough left on the existing drive for ongoing needs.

With the calculations done, enter a figure into the third box (the only box that allows a value to be entered). This needs to be entered in megabytes (MB), so for a 30GB partition enter the figure as '30000'. Click the Shrink button and Vista will shrink the partition; how long this takes depends on the speed of the computer, but it shouldn't be more than a few minutes.

When it's finished a new partition will appear, labelled as 'Unallocated'. Right-click this partition and select New Simple Volume from the window that appears. The New Simple Volume wizard will now appear. Click Next to move on to the first step and then specify how big the partition should be.

Unless creating two new partitions, there's no point leaving space free here so select the biggest possible size and click Next. Now assign a drive letter to the partition. Use the dropdown box to select any of the available letters, then click Next.

The last step in the wizard is to format the drive so it's ready for the installation. Make sure the file system is set as NTFS and the Allocation Unit Size set to Default. Now enter an appropriate name in the Volume Label section, such as 'Windows7'.

Finally, click Next and, in the window that follows, click Finish. The new drive will now be formatted; depending on the size of the drive, this can take a few minutes. When complete, it's time to install Windows 7 on the new drive partition.

Installing Windows 7
The hard work is now done. To install the new operating system, place the Windows 7 installation disc in the appropriate DVD drive and restart the computer. Shortly after powering up, a message like 'Press any key to boot from CD' will appear - do as it says. If you don't and Windows Vista starts loading as normal, the computer's start-up (or boot) settings may need to be changed.

To do this, enter the Bios settings (usually performed by pressing F1 after powering the PC). There are many different Bios menu systems so it's best to consult the computer's manual or contact the manufacturer, but look for an option labelled something like 'Boot Order' and then make sure your CD/DVD drive is top of the list.

When the Windows 7 setup program launches, follow the process as normal. At the point where it asks where it should be installed, be sure to select the newly created partition (it will be listed with the same drive letter/name specified earlier). Be very careful here: select the existing Vista partition and it will be formatted, erasing all your data.

Once the installation has finished, a new Windows Boot Manager menu will appear each time the PC is switched on: this displays all installed operating systems. Using the arrow keys select the one you want to load and press Enter. Fail to make a choice within 30 seconds and the default operating system (ie the one at the top of the list) will be loaded.

Boot order
If, after testing, you decide that Windows 7 has earned its place as the number-one operating system it is possible to change the boot menu order.

Alternatively, you may feel it's time to consign Vista to the history books and get rid of the boot menu altogether, so that your computer always starts up in Windows 7. Either way, it is easy to make these changes.

First click the Start button, right-click Computer and select Properties. On the left of the window that appears, click Advanced system settings. In the new window, select the Advanced tab and click on the Settings button in the Startup and Recovery section.

Using the dropdown menu at the top, you can select the default operating system. This is the operating system that will be loaded if no choice is made when the Windows Boot Manager appears shortly after the computer is switched on.

To always launch into the default operating system, clear the tick from the ‘Time to display list of operating systems’ box. Alternatively, you can adjust how long the menu appears for by changing the ‘seconds’ figure on the left.