Microsoft has released a new test build of its Windows Vista release that is as interesting for what is included now as for what's coming next.

On Monday, Microsoft made available to its 15,000 to 20,000 technical beta testers the second Community Technology Preview (CTP) release of Vista, Build 5231. Company officials said they expected to expand availability shortly of the CTP to include an additional 625,000 Microsoft Developer Network and TechNet subscribers .

The October CTP update includes, as expected, a number of new Internet Explorer (IE) 7.0 features. It also includes some new networking and diagnostics functionality.

But what's equally interesting in the new CTP are the hints about the features that Microsoft is planning to add to later Vista CTP and beta builds.

As many industry watchers were expecting, Microsoft is planning to build the core of its Windows Antispyware product into Vista. While the anti-spyware code – which Microsoft has been beta testing for the past few months -- is not part of the October CTP, the Vista Security Center exposes the fact that Windows Antispyware will be included in Vista, going forward.

Lead Windows product manager Greg Sullivan confirmed that Microsoft is planning to integrate the core Windows Antispyware product into Vista.

"The core Windows Antispyware functionality gets built in," Sullivan said. "For unmanaged environments – home and small business users – we want to provide base-level security services."

Microsoft is still planning to make antispyware and other security add-ons available "out-of-band," Sullivan said, as some kind of add-on products and/or services that will rely on the Windows Antispyware core, he said.

Another new Vista feature that is hinted at in the October CTP build is Windows Media Player 11, the new version of Microsoft's audio/video player that the company already bundles as part of Windows.

While the October CTP includes code that is labeled as "Windows Media Player 11," the actual bits are more like "Windows Media Player 10-plus," Sullivan said. The real Media Player 11 code will be added in a future Vista build.

The Windows Media Player bits that are part of the October CTP are not final yet, but "look really cool," said Robert McLaws, a Windows beta tester and president of Interscape Technologies. "They've made some usability improvements in the UI (user interface), centering the buttons in the player, and making commonly accessed buttons like the play button much bigger," McLaws said.

Microsoft CTP builds are snapshots, intended to provide testers with a glimpse of where particular products are, in between full-fledged beta releases. Microsoft's developer division has been championing CTP releases for nearly a year. The Windows client and server teams both launched their first CTP builds in September at the Microsoft Professional Developers Conference (PDC).

Microsoft's current plan is to release a mid-October CTP, followed by a mid-November CTP. In December, the company is looking to deliver the full-fledged Vista Beta 2 release in December, according to partner sources close to the company.

Microsoft is reminding testers that "many of the features included in the October CTP are still being developed and do not yet represent their final functionality or design," according to a corporate statement. Among the features that Microsoft is warning will "undergo significant changes" before the final version of Vista ships: Migration Wizard, Power Management Center, Windows Antispyware, Windows Calendar and Windows Media Player 11.

Not everything is in as much flux as these features, however. Microsoft has introduced several new pieces of functionality with the Vista October CTP that are more likely to get minor tweaks, as opposed to major facelifts.

Among these new CTP features are: Built-in diagnostics, including memory, disk and network diagnostics; a new Network Center, a central network-management hub that will replace Windows XP's My Network Places and Network Neighborhood; a new Windows Mobility Center management hub; and enhancements to power-management.

The October CTP includes a slew of expected IE 7.0 additions, as well, including the new Internet Explorer ActiveX opt-in feature; a new Favorites center; Quick Tabs; and a shrink-to-fit printing capability.

Microsoft also fleshed out some of the networking details in the new CTP release.

"There are a ton of networking improvements, because that's what they focused on in this cycle," said McLaws. "It looks like they polished off the unified IPv4/IPv6 framework, as the naming has been changed in the 'Network Properties' pane. You can also change the order that certain network services are bound to the network adapter, which is nice."

Although some testers were expecting the Windows Sidebar pane to be resurrected as of the October CTP build, that did not happen. Microsoft officials have said to expect the Sidebar to be part of an undesignated future Vista build. Officials have said that most of the planned Vista user-interface changes will not debut until Vista Beta 2 and later.