Security Essentials for Windows XP will die when the OS does
The antivirus software will stop getting updates, and you won't be able to install it.
There are three months to go for Windows XP. The ancient operating system is leaving extended support on April 8, at which point Microsoft will no longer ship free security fixes. XP itself isn't the only thing that's losing support on that date. The Windows XP version of Microsoft Security Essentials, the company's anti-malware app, will stop receiving signature updates on that date and will also be removed for download.
The message is clear: after April 8, Windows XP will be insecure, and Redmond isn't going to provide even a partial remedy for the security issues that will arise. Antivirus software is just papering over the cracks if the operating system itself isn't getting fixed.
In contrast, both Google and Mozilla will provide updates for Chrome and Firefox beyond the cessation of Microsoft's support. Google has committed to supporting Chrome until April 2015.
With three months to go and Windows XP still holding almost a thirty-percent usage share of the Web, the ending of support is going to have an impact on a lot of people. Still, it's unlikely that killing off MSE is going to be the straw that breaks the camel's back and forces these Windows XP holdouts to upgrade.
The big question is, what will? XP's end of life shouldn't come as a surprise to anyone, but there are plenty of XP users who evidently don't care. There's no chance now that the remaining users will migrate off the operating system in the few remaining months of support. An abundance of insecure, exploitable, and most likely exploited Windows XP machines is now an inevitability.