Microsoft has released the RC version of Windows Phone 7.5 to developers, Microsoft delivered updated developer tools and a new build of the OS to programmers. The question remains, why Microsoft hasn't released the final version of the OS update?

According to Microsoft's Cliff Simpkins, there's a simple explanation. Although Windows Phone 7.5 is completed, the developer tools aren't. SO the pre-release Windows Phone OS build that Microsoft is giving out this week maps to the development toos version, which Microsoft describes as a "Beta 2 Refresh." The company stated previously that it would deliver an Release Candidate version of the tools in late August.

"What we are providing is a genuine release candidate build [of Windows Phone 7.5], with enough code checked in and APIs locked down that this OS is close enough to RTM that, as a developer, it’s more than capable [enough] to see you through the upcoming RC drop of the tools," Simpkins wrote in a blog post announcing the developer releases. "It's important to remember that until the phone and mobile operator portion of Mango is complete, you're still using a pre-release [OS] on your retail phone, no matter the Microsoft build ... [This code] only includes the Microsoft portion of the [Windows Phone 7.5] update."