On Monday, Microsoft responded to persistent rumors about an upcoming new Zune digital media device called the Zune HD. It's real, the company says, and will ship in the United States this fall. But I can be a bit more specific: According to my sources, Zune HD will ship on September 5, 2009.

"This is the next step in our strategy to broaden Zune as an entertainment service for Microsoft," a posting on Microsoft's official Zune Insider blog reads. "We are really excited to bring the new Zune to market later this year, and ... we will be coming to Xbox, taking over the existing video marketplace, and bringing a rich new experience with new features."

The Zune HD is positioned squarely against Apple's popular iPod touch, Microsoft says. It features a 3.3" 16 x 9 widescreen OLED display with a resolution of 480 x 272, but it can output in true 720p HD via a dock and HDMI port. The device incorporates multi-touch functionality with a touchscreen virtual keyboard (like the iPod touch), an accelerometer, HD radio support, a "full" web browser, Wi-Fi with music-streaming capabilities, and integration with the Xbox.

That last bit is potentially the most interesting aspect of yesterday's revelations, since Microsoft has been talking for some time about merging the online capabilities of its popular video game system with the Zune. According to the software giant, the Zune Marketplace will replace the current video and TV purchasing capabilities on the Xbox 360, making it possible for the first time for users of either system to access their collections from multiple device types.

There are still a number of unknowns about the new device. Microsoft hasn't revealed pricing, for example, and although we know that the Zune HD will incorporate flash RAM (and not a hard drive), it's not clear what the exact memory allotment will be. Microsoft says it expects the Zune HD to eventually replace the current flash-based Zune devices, the Zune 8 and Zune 16. The HDD-based Zune models will apparently continue selling, however.

Microsoft says it will demonstrate Zune HD and the new Zune Marketplace functionality on the Xbox 360 at next week's video-game-oriented E3 trade show. The company says that although the Zune HD is US-only (at least at first), the integrated Zune Marketplace experience for the Xbox 360 will be released worldwide.