IBM and Chinese PC vendor Lenovo, the world's fourth-largest computer maker, are actively discussing a plan that would see Lenovo introduce a line of mass-market systems running IBM's "Microsoft-free" software client, InformationWeek has learned.

Lenovo could soon roll out volume PCs bearing the Windows-less client for the consumer and business markets as a result of the talks, according to industry sources.

The Microsoft-free software package features IBM's Lotus Notes and Lotus Symphony e-mail and desktop productivity suites, running on versions of the open source Linux operating system provided by Canonical (Ubuntu), Novell, or Red Hat.

IBM announced availability of the Microsoft-free client earlier this year in Europe. On Tuesday, the company expanded the program to the U.S. market. To date, however, it's been limited to local resellers who cater mostly to small and midsize businesses.

Though nothing is final, Lenovo's participation in the project could vastly increase its reach and pose a significant threat to Microsoft's dominance of the desktop PC market. Lenovo controls 7.8% of the worldwide personal computer market, according to research firm Gartner.

Microsoft-free PCs could appeal to cash-strapped consumers and businesses facing higher operating costs because of the energy squeeze. IBM has said that systems built on its open source client should cost about half as much as Windows PCs. That's because computer vendors that sell Windows systems must pay a license fee to Microsoft for each system shipped and usually pass the cost on to customers.

Linux and Lotus Symphony are both available free of charge.

Word of Lenovo's possible participation in IBM's Microsoft-free program comes at a time when Redmond is vulnerable in the business market. Few large enterprises have upgraded their systems to Windows Vista because of concerns about the newest Microsoft operating system's resource requirements, intrusive security features, and lack of compatibility with older software.

IBM and Lenovo have maintained close ties since IBM sold its PC business to the Chinese company in 2005 for $1.75 billion. Last year, the two vendors expanded a global alliance under which they are cooperating on building IT systems for specific industries.

An IBM spokesman on Wednesday would say only that there is "no reason" why large PC vendors could not participate in the Microsoft-free program, but declined to confirm whether the company is in talks with Lenovo or any other vendors.

Lenovo officials did not immediately return a call seeking comment.

IBM has said the Microsoft-free program began as a response to a request from a group of CIOs from major companies and government organizations in Russia, including Aeroflot and the Ministry of Defense, for low-cost systems built to open standards.