"I'd caution you to recognize that 'licenses sold' and 'licenses deployed' are not the same thing. Licenses are sold with new PCs, but many customers downgrade back to an older operating system aboard professional grade products," IDC analyst Al Gillen said via email.
Gartner analyst Michael Silver said that it's not clear what's the story behind the numbers Reller provided.
"They don't seem to be overly high or overly low that would indicate huge success or huge failure -- and even Vista sold millions of copies," he said via email.
Silver also indicated that "lots of issues" negatively impacted Windows 8's launch, including the delay of many new computers.
"It seemed to be anticlimactic, and there was lots of hardware that could have made it more exciting that was delayed. You get the feeling Windows is treading water until the ecosystem -- and maybe even the next release -- come together," Silver said.
Reller acknowledged in her presentation that the initial supply of Windows 8 touch-based devices -- like tablets, hybrid laptops and all-in-one systems -- was insufficient and that distribution was in some cases improperly allocated. Microsoft has been working on fine-tuning these issues, she said.
According to the Morgan Stanley analysts, Microsoft's business could be helped if the company decides to release an Office version for iOS devices, which could add between $1 billion and $2 billion to the annual revenue. However, Microsoft has been mum on this point, and its reluctance so far to offer Office for iPads and iPhones is seen as a competitive move to help sales of tablets running Windows 8 and Windows RT, the Windows 8 version for devices based on ARM chips.
For now, Morgan Stanley expects Windows' share of the tablet OS market to be 9 percent this year, down from its previous forecast of 14 percent. The company is also adjusting downward its revenue forecast for Windows, Office and other software products. Overall, Morgan Stanley now expects Microsoft's fiscal year revenue and profit to be $79.91 billion and $2.83 earnings per share, respectively, down from the previous forecast of $83.52 billion and $3.01 earnings per share.
Microsoft's stock closed down almost 1 percent at $26.46 on Thursday.
Juan Carlos Perez covers enterprise communication/collaboration suites, operating systems, browsers and general technology breaking news for The IDG News Service. Follow Juan on Twitter at @JuanCPerezIDG.