Shares of Dell fell sharply Wednesday after the No. 2 PC maker trimmed its full-year outlook in a slowing market. By midday, they had dropped 8.5 percent to $14.46, their biggest single-day fall since May 2010.

The slide began late Tuesday after Dell posted second-quarter results along with a bearish forecast for the second half, usually its most profitable period, as companies order new computers and consumers snap them up for holiday giving.

Founder and CEO Michael Dell predicted growth of a meager 1 percent to 5 percent for the period ending in January. That means Dell expects a lackluster holiday sales season as well as a poor order book from the corporate market.

Once primarily a consumer PC vendor that operated via mail-order, Dell now only derives about 20 percent of sales from consumers. The rest is from the corporate market.

The Dell move may also foreshadow Thursday's report from Hewlett-Packard, the biggest PC maker as well as the world's biggest computer company.HP shares fell 4.2% to $31.21.

Dell, based in Round Rock, Tex., reported second quarter net income rose to $890 million, or 48 cents a share, from $545 million, of 28 cents, a year ago, or a penny below analyst estimates. Revenue gained less than 1 percent to $165.7 billion.

"We're pleased with our results in the first half," CEO Dell said after the results were announced.  But CFO Brian Gladden acknowledged "We're saying third quarter feels like flat," noting softer demand from consumers as well as the U.S. government.

Dell also is a minor player in the fast-growing markets for smartphones and tablets. Its Streak 7 phones and Value Pro tablets both have tiny shares of the market, where sales are outpacing overall PC growth.

One of the biggest losers is clearly Dell himself, who owns more than 243 million shares, valued Wednesday around $3.5 billion.