There are just two years to go. Two years to migrate your Windows XP-based PCs to a more modern operating system, such as Windows 7. Two years to enter the 21st century. Two years until XP support is over.

Are you ready?

If you’re coming at this from a medium-sized business or enterprise, chances are the answer is no. And if your Windows 7 migration is still in the planning or pre-planning stage, it’s pretty likely that what’s holding you up has little to do with technological issues. And these are problems that Microsoft, curiously, seems to be ignoring right now.

This week, the software giant acknowledged -- celebrated? -- the two-year countdown to the end of Windows XP support, which will occur on April 8, 2014. (Ditto for Microsoft Office 2003, as it turns out.) “If you still have some PCs running Windows XP and Office 2003 in your organization,” Microsoft director Stella Chernyak wrote in a post to the Windows For Your Business Blog, “now would be a good time to start migrating them to Windows 7 and Office 2010.”

It’s hard getting an exact figure on the Windows XP installed base, but suffice to say it’s still enormous, and in the hundreds of millions range. Looked at as a percentage of all 1.3 billion Windows users worldwide, close to 50 percent are still using XP. And in enterprises, it’s even higher, possibly as high as 65 percent.

Microsoft has a neat way of downplaying the benefits of continued use of XP, by noting that XP was “a great software release for its time” but that the market and people’s expectations have evolved since then. This is certainly true, but as one business owner who wished to remain anonymous told me this week, XP isn’t any less usable today than it was three or five years ago.

It’s a strange problem to have, when you think about it. Windows XP has withstood the test of time in part because it has continued working so well, despite advances in technology that are better taken advantage of with newer Windows versions.

Not helping matters is that Microsoft is working to complete the next Windows version, Windows 8, one that's firmly targeting the consumer market and not businesses. So I’m not surprised to see that Chernyak isn't advising customers to wait for Windows 8. “We don’t recommend waiting,” she writes. “By upgrading to Windows 7 today, [customers] can gain substantial results today while laying the foundation for [Windows 8].”

When you look at the top three reasons why medium-sized businesses and enterprises are still stuck on XP, the number one reason is always application compatibility, which can be divided into two categories: native applications and web apps. Frankly, the native application compatibility story is pretty mature at this point, and I’d be surprised if native application usage were holding up Windows 7 migrations to any major degree. But web apps are another story.

Curious about this, I spoke to Browsium’s Gary Schare. You might recall this company and its compatibility product Browsium Ion, which lets you use multiple versions of Internet Explorer rendering engine profiles, Flash, and Java, all at the same time, in the same browser. (See " IE 6 and the Dark Side of Success" for the details.) Browsium overcomes what I think is the biggest blocker to an XP to Windows 7 migration: web apps that require IE 6. And not surprisingly, Browsium recently scored a big win with HM Revenue & Customs (HMRC), a forward-leaning part of the UK government that’s in the process of migrating 85,000 XP desktops.

“HMRC had hundreds of line of business web apps that needed remediation help before they'd work on modern IE versions and Windows 7,” Schare told me. “They’re a great example of the type of organization that has this problem.”

Of course, Browsium isn’t the only solution for migrating web apps. Microsoft offers various application virtualization solutions, such as Application Virtualization (App-V) and Microsoft Enterprise Desktop Virtualization (MED-V), not to mention more data center-centric solutions based on Virtual Desktop Infrastructure (VDI). But these solutions tend to be complex and expensive.

Looking past the compatibility issue, you might be surprised to discover that the number two and three blockers to a Windows 7 migration -- money and inertia -- have nothing to do with technology at all. Instead, they speak to a simple pragmatic truth that faces companies of all sizes: It’s hard to justify change when what you’re using still works.

XP, in some ways, is the best investment the enterprise ever made, the Windows version that refuses to die. Ironically, it came of age at a time when Microsoft was trying to grow beyond its roots as a maker of systems for smaller companies; in courting enterprises and big business, Microsoft had to extend the lifecycle for its platform offerings far beyond that of older products. And XP’s lifecycle was positively affected by the lateness of Windows Vista, which caused Microsoft to push things even further out.

There’s a dirty little secret in the Windows world that has silently benefitted XP in the business world, too. Although it’s hard to find real numbers for this phenomenon -- given that Microsoft would probably like to pretend it doesn’t happen -- it’s very clear that businesses have been buying Windows Vista and Windows 7 desktops for years and downgrading them to XP before handing them out to employees.

This practice was understandable with Windows Vista, but I’m sort of surprised to discover how common it is with Windows 7 as well. So even in cases in which businesses are spending money on technology such as new PCs, they’re often installing a decade-old OS on the machines after the fact.

With a typical Windows 7 migration taking 9 to 18 months depending on the size of the business, we really are starting to get down to the wire when it comes to the expiration of XP support. And yet I’m not seeing any sense of urgency out there. Two years sounds like a long time. But it’s not, not for this kind of project.

It’s possible that, as some suggest, there will only be single-digit millions of PCs in the world running Windows XP when April 8, 2014, arrives. I suspect it will be worse than that. But either way, when Microsoft does stop supporting Windows XP, there will almost certainly be literally millions of business PCs around the world using it regardless. Work to prevent that needs to happen sooner rather than later.

Are you ready?