It's a near-certainty that no matter where you're reading this from, Windows XP was at one time or another your main operating system at home, work or both. Released to retail in October 2001, the OS remained the most popular in operation until August 2012, when fellow Microsoft product Windows 7 overtook it.

According to data from Net Applications, whose Market Share service keeps track of what operating systems are in use on the Internet, nearly 28 percent of people still log on using Windows XP as of March. But after support for Windows XP ended April 8, any business or person staying with the operating system is at risk for possible cybersecurity problems.

For some, the end of support has been a prime opportunity for promotions. Until June 15, Microsoft is offering consumers $100 off a new computer running Windows 8.1 with the trade-in of a computer running Windows XP. Best Buy is also offering the $100 credit toward any new Windows computer, Mac or Google Chromebook.

For its part, Google has taken the opportunity to sell Chromebooks one step further, offering businesses up to $200 off each Chromebook with the purchase of VMWare Desktop as a Service cloud services. Unlike many PCs or Macs, Chromebooks typically retail between $200-500.

But let's say you, your business or someone you know is inclined to stay with Windows XP and save a few dollars on upgrades for the time being. After all, the British government has chosen to keep its Windows XP machines, paying Microsoft approximately $9.25 million to extend support for one year for its employees.

What risks are present for those who take the leap of faith and stay with the 12-year-old OS?

Despite its age, some 700 vulnerabilities big and small have been discovered by Microsoft throughout XP's lifespan. Now, without the Redmond, Wash.-based tech giant issuing patches and fixes for those flaws, it's an unfortunate likelihood that not only new insecurities will emerge, but that hackers will reverse-engineer past "Patch Tuesday" Microsoft updates.

Depending on the industry, the consequences are potentially dire for businesses.

In the healthcare world, many important medical devices still run XP. In an interview with HealthcareInfoSecurity, medical device researcher Kevin Fu called XP a "dominant operating system" with devices in hospitals.

For the financial realm, ATM-maker NCR estimates that just one-third of the world's ATMs have made the transition from Windows XP. That statistic isn't quite a cause to get to your bank and withdraw all your money, however.

"Most bank ATMs are very well protected," writes KAL ATM Software CEO Aravinda Korala. "They are connected on a private network with no Internet access. They are locked down tightly so that only the minimum functionality necessary for the ATM to operate is allowed."

The largest banks in the world have agreements with Microsoft along the lines of the British government, paying for additional support. Yet, many small banks and credit unions might be in serious trouble if a yet-to-be-discovered virus hits.

Infrastructure systems such as power grids, oil and gas refineries, chemical plants and various other utilities are also common users of XP. The exact percentage of industrial control systems using the OS is unknown, but Jonathan Pollet, founder of Red Tiger Security, was quoted in The Christian Science Monitor as saying it may be up to half.

On a federal level, the Department of Homeland Security's Computer Emergency Readiness Team has sounded alarms about the dangers to control systems, releasing a March report outlining the risks involved in industrial users using the OS, as well as the prospect that such facilities may be running afoul of regulatory compliance.

Back in 2007, Microsoft warned that it would cease support for XP in the coming years. The fact that the eventual end-of-life date came in the spring of 2014 is a testament not only to XP's popularity and shelf-life, but also to the struggles of Microsoft in recent years and its roundly criticized Windows 8 system.

Yet, now that the day of no support has come, even die-hard loyalists to the OS should protect themselves against inevitable problems.