So what happens now? You can, of course, continue using your PC running the creaky-at-the-knees operating system, but doing so ramps up the risk to your security and privacy.
Over time, support for your favorite apps will end too, so perhaps an alternative approach is called for.
That approach obviously means moving on from Windows XP, either to a new version of Windows or even a completely different platform.
But what does the future hold for your trusty old PC? Read on to find out what to do with it should you decide to finally part ways with XP.
1. Upgrade it to Windows 7 or 8
If you're still attached to your old PC – perhaps for financial reasons – then ask if you might be able to upgrade it to a later version of Windows. The obvious candidates are Windows 7 and 8, because both will be familiar to you, and don't have demanding system requirements.
If your PC has a 1GHz or faster processor, 1GB RAM, 20GB free hard drive space and a DirectX 9-compatible graphics card or chip, it'll work with the newer version of Windows. Performance won't be as fast as in XP, but it should be acceptable, particularly if you don't run too many programs at once.
Before taking the plunge however, download and run either the Windows 7 Upgrade Advisor or Windows 8.1 Upgrade Assistant to get a more detailed compatibility report – you may find the cost of upgrading or replacing different parts of your PC is more expensive than simply replacing it.
2. Replace it
A new desktop PC with Windows 8 pre-installed can be purchased for under £265 (US$300, A$500). If you decide the end has come for your old Windows XP PC, make sure you dispose of it carefully and responsibly.
Once your new PC is up and running, wait until you're happy you've transferred over all the documents, files and other data you need from your old PC before taking steps to securely shred all personal data from the drive.
If you're planning to pass the computer on to someone else, use a free tool like Eraser to wipe sensitive files from the drive, then restore it to its factory settings before using Eraser to securely wipe any free space for added security.
If you plan to dispose of the computer, use Darik's Boot and Nuke tool to create a bootable CD that will completely wipe the drive of all data, allowing you to then take it to your local recycling center or pass it on to a charity such as Computers 4 Africa.
3. Switch to Linux
If you're looking for a modern OS to replace XP that will run smoothly on your old PC, then Linux is the answer. We'd recommend that you choose Ubuntu as your Linux distribution of choice, and download the latest LTS version, currently 12.04, which will be supported until 2017.
4. Your personal cloud
One way to keep your old PC working for a while longer is to convert it for use as a dedicated server of some kind. If it's a low-powered laptop, then a great use for it would be as your personal cloud device, allowing you to back up, archive and store documents and other files away from your new computer.
5. Build a media server
Another possible use for your old PC could be as the focal hub for your videos, photos and music, collecting them together in one convenient central location and then piping them over the network (and wider internet) to other devices, including computers, tablets, phones and even smart TVs and set-top boxes. Check out our guide to building a Raspberry Pi server, substituting your old PC for the Pi.