Sept. 9 (Bloomberg) -- Dell Inc. founder Michael Dell bought $100 million of shares last week after the personal-computer maker's stock plunged following disappointing earnings.

Dell, the chairman and chief executive officer of the Round Rock, Texas-based company, bought about $71.5 million of shares on Sept. 4, and $28.5 million on Sept. 5, according to a regulatory filing yesterday. As of July 1, Dell had a 12.8 percent stake, making him the biggest shareholder.

Profit last quarter missed analysts' estimates as the world's second-largest PC maker said the U.S. slump in technology spending had spread abroad. The company has cut prices and increased sales through retail outlets to boost revenue and take market share from leader Hewlett-Packard Co.

Dell plunged the most in almost eight years on Aug. 29 in Nasdaq trading after saying that ``continued conservatism'' from some U.S. clients had spread to Europe and Asia. Dell has fallen 26 percent in the past 12 months. Its consumer business posted a $5 million loss in the second quarter as the company struggled to reduce manufacturing costs in line with price cuts.

Dell fell 87 cents, or 4.3 percent, to $19.30 at 4 p.m. New York time in Nasdaq Stock Market trading. The shares have declined 21 percent this year.

The Wall Street Journal reported last week that Dell was planning to sell its computer factories to help cut $3 billion in costs and revive profit margins. Dell may sell the plants within 18 months and has approached contract computer manufacturers, the newspaper reported. Once known for its manufacturing efficiency, Dell has fallen behind as Hewlett-Packard wrung savings from Asian contractors.

Michael Dell paid $20.42 a share for 3.5 million shares on Sept. 4, and $20.67 for 1.38 million on Sept. 5. On July 1, the CEO paid $47.6 million for 2.17 million shares. He spent $2.19 million on 100,000 shares on June 30 and $49.9 million on 2.23 million shares on June 27.

Jess Blackburn, a spokesman for Dell, declined to comment.

To contact the reporter on this story: Kristen Schweizer in London at Kschweizer1@bloomberg.net

Last Updated: September 9, 2008 16:16 EDT