What’s the biggest threat facing Windows 8 in today’s marketplace? Is it the rise of Apple? Is it perhaps the move away from desktop computing? All of these things may be contributing, but the biggest threat may just be that nobody knows or cares about it.

The AP and market research firm GfK recently surveyed 1,200 US adults over the phone about Windows 8. The big takeaway – 52 percent of respondents have never heard of Windows 8 despite Microsoft’s $1.5 billion marketing blitz.

Such a higher number may be cause for alarm, but Microsoft may have already accounted for the kind of people that don’t follow operating systems too closely. What they should be worrying about it are those who knew about Windows 8 since its introduction over two years ago. The survey found that 61 percent of those who knew about Windows 8 have no interest in upgrading. Even more damning, only 35 percent believe it’s an improvement over Windows 7.

The folks at Microsoft have their work cut out for them over the next few months as they try to sell the new operating system to consumers and enterprise customers alike. Early reception has been mixed with some enterprise customers adopting the new operating system for its consumer-friendly tablet integration. Others are reluctant due to the amount of retraining required to get employees up to speed.

Windows 8 was never a solid sell for desktop users, but Microsoft can still pull out a success in the mobile market. The company’s Surface tablet seems to be doing well with early adopters and the Windows Phone 8 event scheduled for later today will shed some light on Microsoft’s strategy with smartphones, a market that it has consistently failed to gain a foothold in.