Before we can begin, you'll need to make sure you have the following three things:
VirtualBox: Other virtual machine programs are out there, but this one has a lot going for it — it's got all the features you need, it's easy to set up and use, and (best of all) it's totally free for personal use. You can pick it up at www.virtualbox.org. Once you're at the site, just click on the download link, then click on the link that says "x86/amd" next to the line that reads "VirtualBox [version number] for Windows hosts."
Windows XP Installation data: In order to install windows on your new virtual machine, you'll need your Windows XP installation disc, or a downloaded .ISO file with the data that comes on that disc.
A Windows XP Serial Key : Just like any other Windows machine, you'll need a serial key to use Windows XP in your virtual machine. If you bought your PC with Windows XP already installed, the product key is most likely on a sticker somewhere on your PC or with any documentation that came with it. If you installed Windows yourself, then hopefully you kept the product key that came with the installation disc. If you didn't, you can still recover your CD key by running Magical Jelly Bean Keyfinder on the system running XP.
If you've got all of the above, start by installing VirtualBox. There's a few choices you can make during the installation, but you can just leave the default options selected for everything and click through. When the installer is done, VirtualBox will start up, and you'll see a message informing you that you don't have any virtual machines created yet. To remedy that, click on the blue New button in the top left corner.
You'll now go through several pages of setup for your new virtual machine. On the first page, choose a descriptive name (such as "Windows XP Virtual Machine") and select what make and model of operating system you're going to install. Conveniently, Windows XP is the default choice, so unless your dropdown menu looks different, stick with that.
The second setup page asks you how much of your system memory you want to devote to the virtual machine while it's running. Windows XP's memory requirements are very low, but for better performance you'll want to increase this higher than the recommended 192 MB. Depending on how much memory you have to spare, you can allocate from 512MB to 2GB. Click Next.
On the next page, leave "Create a virtual hard drive now" selected and click Create. A new setup window will open, with choices about virtual hard drive files. Leave the default "VDI" option selected, and click Next. On the following page, choose Dynamically allocated, which means that you can allocate, say, 25GB of hard drive space for the virtual machine, but that space won't actually be used up on your physical hard disk unless you actually use it for something in the virtual machine. Click Next again.
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