These are busy times for plucky PC maker Apple Computer (NASDAQ:AAPL), which is scheduled to release an updated version of its OS X operating system later this month and will report quarterly results later this week.

But while both of those stories are certainly of interest to Apple users and investors, the media is instead waiting impatiently for Thursday when, it is expected, the next verse of the iTunes opera is expected to be heard for the first time. Speculation is rampant that a planned press event will mean the unveiling of iTunes for Windows users.

The service found a ready army of supporters pretty much from the get-go. Gushing profiles of the service and the minds behind it have filled magazines across the globe, anointing it as one of the first meaningful steps in closing the divide between digital music users and the recording industry. I've seen firsthand the reason people like iTunes: Scanning, previewing, and purchasing music couldn't be easier. Exclusive songs are an added bonus and the pricing is reasonable. When paired with a high-speed Internet connection, it can be quite addictive.

iTunes faces increasing competition from the likes of Napster, set to be relaunched by Roxio (NASDAQ:ROXI) later this month, and RealNetworks' (NASDAQ:RNWK) Rhapsody service. While all three are (or are expected to be) similar, iTunes clearly has the lead in publicity -- no surprise, as the company has never had trouble getting attention, at the very least, for its ideas and products.

What stands to take iTunes to the next level -- beyond constantly expanding its catalog of music and, hopefully, making it easy to find new and lesser-known artists -- would be availability for Windows users. (While Apple's popular iPod handheld is Windows-compatible, the files sold on iTunes aren't -- you currently have to stock your iPod with files in Windows-compatible formats such as MP3.)

Clearly this long-anticipated move would provide a huge new sales opportunity for Apple. It would, however, also present a considerable -- and familiar -- marketing challenge: how to get users raised on another standard to come over to the "other side."

Dave Marino-Nachison is addicted to MP3.com, but he doesn't own shares of any of the companies mentioned in this story. He can be reached at dmarnach@fool.com.