The recent release of the Windows 8 operating system was thought to bring a lot of added value to PCs by opening up several exciting new possibilities, complete with some terrific touchscreen integration.

But a recent study from the NPD Group (News - Alert) suggests sales of PCs in the United States didn't get a whole lot more help from the release of the new operating system, as the total sales of Windows devices actually fell from the same time a year prior.

The NPD Group's report analyzed sales for the time around the Windows 8 launch and compared them against the numbers from the same time a year prior, and discovered that the sales of Windows PCs and tablets had actually fallen off from the previous year, and by a pretty healthy margin: fully 21 percent.

But the NPD Group was quick to note that there was no sign – specifically that Windows 8 was responsible for the fall-off in sales. Rather, the NPD Group is interpreting the drop in sales to a growing trend in which more people are turning their interest to smartphones and tablets rather than upgrading their PC hardware.

While it's not hard to share the NPD Group's stance up to a point, there's a point they may not be considering. Yes, more people are making the move to smartphones and tablets, but PCs are surprisingly durable pieces of hardware. There are some out there who are using the same desktop they bought seven years ago as it still meets most of their requirements. Others still buy mainly used PCs, because they don't need the latest and greatest, but rather a step up from their last model.

When they're working on a five-year-old PC, getting the top-of-the-line from two or even three years ago seems like a quantum leap forward. Meanwhile, smartphones and tablets improve on a fairly regular basis – though to what degree they improve is debatable – so making smaller purchases more frequently is the order of the day in that field.

The PC market may be losing sales, but there's a fair chance that some of that is just a broadening of the overall purchase pool, as opposed to people throwing over the desktop for the tablet and smartphone. While only time will tell if this is indeed the beginning of the post-PC era that Steve Jobs (News - Alert) was so fond of discussing, or just a change in the market, what's clear is that Windows 8 hasn't yet proved enough of a draw to light a fire under sales.

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