Well, you'd better mark your calendar --you have until April 8 to replace it because Microsoft said it's ending support and updates for XP. Without patches and updates, your computer has an increased vulnerability to viruses, hackers, spyware and all sorts of unpleasant things that may make you wish it would just explode and be done with it.
It's only about a month away so you may want to think about updating to Windows 7 or 8. Windows 7 has almost half the market share -- if you're comfortable with XP, it's a lot easier to transition to Windows 7 than it is to 8. Microsoft has generously created a Windows XP data transfer tool to aid in your migration.
Ease of use may be the reason why Windows 8 is languishing, with slightly more than 10% market share. For my purposes, Windows 8 and 8.1 is the same thing, although Windows 8.1 makes up 40% of 8's 10% market share and hasn't officially been released. It's scheduled to be released on April 8, the exact same day XP is left twisting in the wind.
For XP users trying to decide between which version you should now use, I suggest either moving to Windows 7 or wait for Windows 8.1. Forget about 8.0 because it will make you want to unplug your computer and drop it on your foot, which will be much less painful than trying to figure out Windows 8. I would rather take a trip to the dentist than attempt to work on a Windows 8 machine.
The advantage of waiting and pushing your luck through XP's zombie phase for Windows 8.1 is the latest update is supposed to have a look and feel similar to Windows 7 and XP. It's designed for computers using a keyboard and mouse.