New York: In response to customer feedback, Dell Inc. is launching three computer systems, including one notebook with a pre- installed open-source Linux operating system. The computers are priced at $599 and will have the Ubuntu 7.04 Linux system.

Linux is the most popular variant of open-source software. Unlike proprietary software, open-source software lets developers share code and add functions, and users only pay for custom features, maintenance and technical support.

Earlier this month, Dell joined collaboration between Microsoft Corp. and Novell Inc. to allow Linux software to work with Windows on computer servers.

In another development, Dell has announced plans to start selling personal computers through Wal-Mart. The move marks a major push by Dell into the retail market after years of relying on direct sales through the mail, phone orders and the Internet.

Dell hopes to improve its sales against rival Hewlett-Packard, which overtook Dell last year as the world's biggest PC maker.

Initially the computer maker will sell its lowest-priced Dimension multimedia desktop computers, also available directly from the computer maker, through about 3,500 Wal-Mart and Sam's Club stores in the US, Canada and Puerto Rico.

They will be sold bundled with accessories for less than $700, from June 10.

Dell spokesman Bob Pearson said, "In the coming quarters, there will be additional activity in support of this move into global retail. Today's announcement with Wal-Mart represents our first step. Stay tuned."

Michael Dell, 41, who established Dell Computers in 1984 while at college, returned to lead the firm as chief executive, after having left in 2004. Though Dell left the top job in the firm he stayed on as chairman, a position he retains during his second stint as CEO.

Dell founded the company with $1,000 and an untried idea in the computer trade - to bypass the middleman and sell computer systems directly to the customer, pioneering his 'direct model'.

Dell's direct sales model, which allows businesses and consumers to buy equipment directly from the computer maker, turned it into a leading computer manufacturer and a Wall Street powerhouse with successive successful earnings announcements. In 1992, Dell became the youngest CEO ever of a Fortune 500 company.

In recent years, however, Dell has been hurt by a glut of low-cost, low-profit PCs and weaker-than-anticipated sales of its pricier, more lucrative desktops and notebooks.