Michael Dell buys $100 million in stock

Shares in Dell rose 4.5 percent Wednesday, the day after Dell's investment was disclosed, but they settled back to close at $22.70, for a gain of 52 cents or 2.3 percent.

According to a regulatory filing the company made after the close of trading Tuesday, Dell bought more than 4.5 million shares for $99.7 million in three separate deals from June 27 through Tuesday.

The splurge leaves him owning more than 250 million shares directly or indirectly, close to 11 percent of the company's stock for a total value at Wednesday's close of more than $5.6 billion. That amount doesn't include options Dell holds on still more stock.

Dell founded the company in his college dorm room in 1984. It grew to be the world's largest maker of personal computers but lost that title to Hewlett-Packard Co. in 2006.

Dell, who had stepped aside as CEO, resumed the job in January 2007 after the Round Rock-based company's growth slowed. Dell is increasingly selling machines through retailers instead of directly to customers over the phone and the Internet.