(NBC) - After 12 and a half years, Microsoft's support for Windows XP, its most popular operating system, has ended.
But millions still use it; as many as one in four PC users by some accounts.
What happens now that Microsoft has washed its hands of XP and you haven't upgraded to a new computer or new operating system?
This means there will be no more patches or tech help from Microsoft. But your PC still works, it's just unsupported. Sort of like having your car go out of warranty after 50,000 miles.
To understand your options, start with this special web page from Microsoft. Also, check out this question and answer page. But understand: Microsoft wants you to buy Windows 8 to replace XP. And if you have an older computer, it probably will not work. So that may also mean a new PC.
If you decide to keep XP and your old computer, sites like the Tech Support Guy can help. Free, run all by volunteers, it lets you ask questions and get help. There's a whole area devoted just to Windows XP issues.
But what about protection from hackers and viruses? Microsoft will provide virus protection for XP through its free security essentials program for one more year, but private antivirus companies like AVG and Kaspersky Lab will also continue to provide virus and Malware protection for Windows XP machines.