A mere three months ago, security support for Microsoft Windows XP finally came to an end.

Most everybody knows this because Microsoft made a lot of noise about it. Microsoft did that because customer pressure kept XP alive longer than Microsoft wanted. Without that pressure, the end for XP would have come sooner and quietly. I think the experience of an operating system that had a 12-year supported span has stiffened Microsoft's resolve not to let it happen again.

Because I knew that the end of XP would be traumatic for some, especially those that are still running XP and really don't want to change, I ran a countdown timer here on my site for a little over two years. The intent was not to rub salt in wounds but rather to emphasize that the end of XP was date certain after several reprieves and that action truly was needed.

But that's not the end of the story. The raw truth is that these end-of-life dates for Windows are set almost the second the product rolls out the door. So far, the extended support period during which security updates will be available is 10 years, as shown here:

A similar schedule is in place for Microsoft Office. New versions of Office launch in the general timeframe of a version of Windows and therefore expire on or about the same date. For example, support for Office 2010 is scheduled to end in October, 2020 along with Windows 7.

There is little doubt that converting from Windows XP to Windows 7 or 8 can be difficult, even challenging. I have one client using 1997 software in Windows XP, software that will not run in Windows Vista or later. That client has reached an emergency state now because the next computer death will bring with it a new version of Windows on the new PC. The project to advance the old software is finally, belatedly, under way but remains troublesome. The delay in working this out is now affecting business and, not coincidentally, raising support costs.

While converting from Vista to newer Windows versions will probably not be as challenging, the XP experience makes it clear that waiting until the last minute is a bad idea. I have therefore launched a new version of my XP countdown timer, found on a few pages throughout my site, that now counts down the days remaining until the end of extended support for Windows Vista. It starts today at 999 but don't be cavalier about that. Those who kept thinking that the end of XP was in the future woke up one morning to find themselves in that future.

And although my clock has its sights set on Vista, don't forget that the clock is running on every version of Windows. So to keep track of Microsoft's schedule, which could always change, visit these pages:

• Windows Lifecycle Fact Sheet
• Microsoft Office Lifecycle List