REDMOND, WA — Microsoft Corp. may unveil the next incarnation of its ubiquitous operating system, cleverly code-named Windows 7, as soon as the second half of 2009, according to a development roadmap recently released by the company. Previously, Windows 7 was not expected to be available until some time in 2010.Windows 7 is expected to be the last Microsoft OS that will support 32-bit computer architecture.

The apparent rush to get the new product on the market may be due at least in part to the disappointing adoption rate of Vista, the current Microsoft flagship. Vista, the much-maligned successor to Windows XP, has underwhelmed consumers since its release in November 2006. While XP generally was hailed as a considerable improvement over previous versions of the OS, Vista incorporated a snazzy new user interface but quickly became known for its temperamental, bloated code, its inappropriateness for laptops (particularly because of an insatiable appetite for battery power and system resources), and the inclusion of much-touted features only very few “power users” wanted. In addition, Vista’s edition hierarchy — Enterprise, Business, Home Basic, Home Premium, and Ultimate — seemed somewhat arbitrary and confusing to consumers, who had embraced XP with gusto.

According to the roadmap, three “milestone” Windows 7 builds are planned for 2008. The first, M1, already has shipped to key partners for code validation, according to APC magazine. M2 is expected to ship in April or May, and M3 should appear during the third quarter. “There’s no available roadmap information about further milestone, beta or release candidate builds, except the updated [release-to-market] date,” APC noted.

If Windows 7 is released in 2009, it will represent a departure from Microsoft’s usual schedule. Typically the company attempts to keep desktop OSes roughly in sync with updated versions of Windows Server, which in recent times have emerged from Redmond about every four years.

Windows 7 is the seventh desktop OS to be based on the Windows NT codebase. (The previous iterations were the original Windows NT, Windows NT 3.1, Windows NT 4, Windows 2000, XP and Vista.) Although Microsoft hasn’t confirmed it, personnel assignments have led to speculation that Windows 7 will incorporate a pared-down, cleaner UI. Julie Larson-Green, who managed Office 2007’s radical transformation, has been tasked with leading the same charge in Windows 7’s development.

As APC writer David Flynn observed, “Few could argue that Windows isn’t in need of a similar cleanup job — the iconic overload of Vista’s Control Panel is a prime example of a once-friendly UI turned feral.”

Features also on the drawing board for Windows 7 include a streamlined kernel (nicknamed “MinWin”) and a built-in virtual machine for running legacy applications. It also may include a relational file system called WinFS, which incorporates native support for XML and sits on top of NTFS, allowing users to store, access and manage their files based on relationships between data. Originally slated for inclusion in Vista, WinFS became an early casualty in Vista’s development due to speed issues.

That shouldn’t be an insurmountable obstacle for Windows 7, which is expected to be native to quad-core processor hardware with Level 3 cache. The much-higher-powered architecture is expected to replace the current dual-core design in plenty of time to make Windows 7’s debut a cause for celebration. Also encouraging for the OS, particularly in light of Vista’s obscene taste for memory: 4GB of RAM (instead of the current 1GB) likely will be the entry-level standard for new desktop systems, possibly as soon as the end of this year.

Hopefully Windows 7 also will include better security features. According to Qualsys, Microsoft software across the board is loaded with vulnerabilities, and the proclivity to succumb to infection seems to be increasing. In 2007, Qualsys identified more than three times as many flaws in Microsoft products as it discovered in 2006, the company announced Wednesday.

The most vulnerable of Microsoft’s applications, according to Qualsys, are Excel and Word, which increasingly are being used to transmit malware via email attachments.