When purchasing my new computer running Windows Vista the salesman said that the computer was not capable of running dual-operating systems. However, I would now like to install my existing copy of Windows XP on the computer. Will this work, or are there some computers which are simply incapable of running multiple operating systems?

Unless this computer has a very particular configuration then it should be capable of running multiple operating systems, since generally all computers have this ability. However, setting-up multiple operating systems on the computer can be quite an involved process and may make you reconsider whether this is the best course of action. In order to run multiple operating systems you must partition the hard drive. Partitioning the hard drive essentially involves dividing the hard drive into segments – allowing one physical drive to be subdivided into multiple segments. Each of these segments is viewed as one logical drive by the operating system. For example, a 500 GB hard drive can be partitioned into 5x 100 GB partitions and each will be seen as a separate drive within Windows (or whatever operating system you are running). The size of the partitions are arbitrary and up to you, and you don’t even need to have each partition the same size (using our previous example, one partition could be 400 GB and another could be 100 GB). Likewise, you don’t even need to have multiple partitions on the hard drive. Most computers only have one partition, meaning that on a 500 GB hard drive you have one 500 GB partition and that’s what is viewable to the operating system.

However, some computers may have a hidden “recovery” partition. This is usually found on brand-name computers and is a special system partition that stores the computer’s recovery data, such as the Windows installation files, drivers, etc. If you ever need to reinstall Windows you simply follow the instructions which came with the computer to boot from the recovery partition which will then reinstall Windows files back onto the main system partition used to host all of the operating system files.

As you can see, running multiple operating systems is conceptually not particularly difficult since you just need to have each operating system stored on a separate partition. However, the difficulties arise when attempting to implement multiple operating systems, particularly when attempting to partition the hard drive. The partitioning of drives is generally done when nothing is on the drive, as this allows the entire partition table (the metadata on the drive specifying how it has been partitioned) to be removed and then created from scratch with the required partition information. If you already have partitions on the drive then in order to create new partitions (for example, to install another operating system) there is generally no free space as the existing partition(s) occupy all the space on the drive. Therefore, before creating the new partition you need to resize the existing partitions to create free space. This is more difficult than it sounds, since often data will be stored all over the partition so it isn’t a simple case of “chopping off” the unused portion at the end of the partition but instead all the data needs to be moved near the beginning of the partition allowing the unused space to be reclaimed. It’s a bit like rotating a half drunk bottle of coke from a horizontal position to a vertical position, moving all of the coke to the bottom of the bottle leaving free space at the top. Windows does not support non-destructive repartitioning so you would need to use a third-party utility for this purpose. Furthermore, it can be a risky proposition as repartitioning is always fraught with potential danger involving loss of data. Therefore, before embarking on this procedure I would recommend that you backup any important data that you wish to keep just in case things go wrong.

Considering for a moment the reason that the salesman said your computer would not support multiple operating systems, this could be related to having a hidden recovery partition on the hard drive. If you are repartitioning the drive and there is a hidden recovery partition present, you need to be extremely careful that you do not remove that hidden partition – don’t get caught thinking that the hidden partition is free space. If you remove that hidden partition then you are also removing all recovery data for your computer, making it impossible to reinstall Windows. Another possible reason for the salesman’s comment could be because if you decide to do a destructive repartition of the hard drive (i.e. remove everything from the drive and then do a clean repartition and reinstallation of the operating systems) the recovery partition (or disc, if the computer came with recovery CDs instead) may repartition the hard drive automatically and then reinstall Windows, thus preventing you from manually specifying the partition configuration.

As you can see, doing a destructive repartition could be suitable in some cases but not others, whereas while a non-destructive repartition could be a bit more costly (as you will need to purchase some third-party utility for the purpose) it is likely to be more convenient and work in more situations. Therefore, my recommendation would be to do a non-destructive repartition of the drive. That said, you must ensure that all important data has been backed-up prior to conducting the repartitioning, just in case something goes awry during the process.

Once the repartitioning has completed you will need to install the second operating system – Windows XP. Be aware that once Windows XP has installed it is possible that it will overwrite the system boot information, resulting in Windows XP always booting and never providing an option to boot into Windows Vista. Should this occur then it should be fixable by booting off the Windows Vista DVD and then performing a repair, which should repair the boot information and also detect the installation of Windows XP, resulting in a boot menu being created allowing you to select which operating system should be booted when the computer starts.

As you can see, the process for installing and booting multiple operating systems on one computer is quite involved and I would not suggest that you attempt any of these procedures unless you can do this in slow time and have a full backup of all data on your computer, just in case things don’t go to plan and you need to complete a full reinstallation of Windows and all data on your computer. If you are not comfortable with this process, or are still unsure whether your computer does actually support dual-boot, then I suggest that you talk with the computer manufacturer to double-check the information and ensure that you are not trying to accomplish something that your computer is simply not capable of performing. I am sure that you could also take your computer to an authorized repair centre to have this work conducted if you do not wish to attempt it yourself.