So far, Microsoft's Windows 8 and Windows RT (the tablet version of the operating system) aren't doing what the company had hoped. CEO Steve Ballmer said that sales of its Surface tablet are "starting modestly" while one independent report claims that Windows 8 sales are well below projections. And according to highly-regarded former analyst and now venture capitalist Mary Meeker, Android and iOS mobile sales will begin to bury PC sales by next year.

If you're a developer or tech entrepreneur, does that mean giving up on what has been the standard desktop platform standard? Only if you want to lose an enormous opportunity to conquer a large market. Here are three important considerations if you've been giving Windows short shrift.

Microsoft will sell tons of Windows 8.

Even with a slow start, it is almost inconceivable that Microsoft won't sell hundreds of millions of copies of Windows 8. It will be the operating system it provides to hardware manufacturers. And even with the business pain that the likes of HP and Dell have found themselves in, companies will continue to buy PCs. So will consumers.

So what if the rate slows down? Meeker forecasts 100 million Windows devices shipping--each quarter. Say that she's wildly over-estimating and cut the number by half. That would still be a market of 200 million by the end of 2013. Big enough for you?

Windows RT apps work for Windows 8 as well.

Windows 8 runs RT (tablet) apps, even though RT doesn't run regular Windows applications, other than Microsoft Office. That means if you target the tablet, you get both devices at the same time, which means at least 200 million by the end of next year. So, by making the right choice, you potentially reach all the users who might be out there.

Again, is that a big enough market?

The current RT app market is pathetically small.

I don't have official stats on this, but I recently purchased a Windows 8 convertible notebook/tablet and browsed through the entire apps store. Easily. There simply isn't a whole lot there.

A lack of apps might be a problem if you want consumers or businesses to adopt your platform--if you're RIM, say, or even Microsoft trying to sell Windows Phone. But Windows 8 will be (conservatively speaking) everywhere. There's very little competition and you have time to stake out good positions in software product categories.

Sure, you could spend your time chasing the iPad and iPhone market, or the Android hardware army. Both have so many apps that new ones typically get buried.

The Windows 8 app market is one that should be large and yet has the opportunity of the early iPhone days. Sure, you need to figure out how to monetize. That's a problem on every platform. But with these types of numbers, it behooves you to find a solution, because the result could be a very nice business.