Surely you’ve already upgraded to Windows 8.1, which provides a significantly improved experience over Microsoft’s original ill-fated touchscreen-centric operating system. If you have, good for you, and if you’ve upgraded to Windows 10, even better. If you haven’t upgraded, however, then you might want to consider making the leap: tomorrow, January 12, 2016, is the last day that Microsoft will be issuing security patches for Windows 8 (via PC World).

You might be wondering how Microsoft can get away without issuing updates so soon after releasing Windows 8. The reason is simple: while Microsoft promises to keep an operating system secure for a full 10 years, in general, they only promise two years of security updates when an OS has received a service pack. Surprisingly, although Windows 8.1 brought considerable changes, Microsoft still considered it a service pack:

“Software updates are evaluated on a case-by-case basis to determine whether they meet the definition of an upgrade, which may require revenue to be deferred and recognized when the upgrade is delivered,” Microsoft stated in a Form-10K filing. “Windows 8.1 will enable new hardware, further the integration with other Microsoft services and address customer issues with Windows 8, and will be provided to Windows 8 customers when available at no additional charge. We evaluated Windows 8.1 and determined that it did not meet the definition of an upgrade and thus have not deferred revenue related to this planned release,” Microsoft explained.

Windows 8 is only used by a small fraction of overall users (around 3%), but if you’re in that tiny minority, then this is important news to you. In short, if you can upgrade to Windows 8.1 (or Windows 10, of course), then now would be the time to do so. Otherwise, you might find yourself facing a cold, hard world full of malware and other nasty business without any protection from Microsoft.