Chipmaker Advanced Micro Devices Inc. posted a disappointing earnings report, and computer maker Dell Inc. warned that its quarterly results would likewise fall short of expectations. Yet Microsoft Corp. beat analysts' forecasts, and investors were cheered on the announcement of its stock buyback.

The mix of news out of tech failed to clear up any of the uncertainties Wall Street faces regarding corporate earnings. Meanwhile, Federal Reserve Chairman Ben Bernanke's testimony on Capitol Hill this week was seen as bullish on the economy, but also a warning that inflation is gaining traction and that more interest rate hikes are likely.

"The market's becoming very, very touchy, very news sensitive," said Hugh Johnson, chief investment officer at Johnson Illington Advisors. "If it's good news, the market goes up. If there's even some bad news, the market goes down. And it's because politics, economics and earnings are all dark clouds hanging over this market."

Crude oil prices, cited by Bernanke as an inflationary pressure, edged higher today as the crisis in the Middle East escalated. A barrel of light crude settled at $74.43, up 16 cents, on the New York Mercantile Exchange.

The Nasdaq dropped 19.03, or 0.93 percent, to 2,020.39 after plunging 41.29 yesterday. It was the lowest finish for the Nasdaq since May 17, 2005, when it closed at 2,004.15.

The Dow Jones industrial average fell 59.72, or 0.55 percent, to 10,868.38, while the Standard & Poor's 500 index lost 8.84, or 0.71 percent, to 1,240.29.

Trading volumes were particularly high due to the expiration of options contracts, which causes a flurry of transactions as those contracts are filled and new ones created. Declining issues outnumbered advancers by about 2 to 1 on the New York Stock Exchange, where preliminary consolidated volume came to 2.8 billion shares, compared with 2.55 billion traded yesterday.

Bonds edged lower, with the yield on the benchmark 10-year Treasury note rising to 5.04 percent from 5.02 percent late yesterday. The dollar lost ground against other major currencies, while gold prices also fell.

Wall Street's wild ride this week, with major rallies and selloffs encapsulated in single trading sessions, reflects the continued confusion plaguing investors. With corporate earnings a mix of disappointments and pleasant surprises, and inflation data showing consumer prices creeping higher, traders have found few patterns to support either buying or selling.

For the week, the Dow gained 1.2 percent and the S&P 500 added 0.3 percent, while the weakness in tech earnings led the Nasdaq 0.83 percent lower.

"We certainly think we're going to be in a volatile market, and we'll be in this wide and sloppy trading range for the foreseeable future, perhaps for the entire summer," said Jack Caffrey, equities strategist at J.P. Morgan Private Bank. "Investors are very much in a reactive mode, and that'll create the choppy trading you've seen."

AMD's earnings added to the concerns about the once high-flying tech sector after the chipmaker reported a quarterly profit that, despite rising eight-fold, came in below analysts' forecasts. AMD dropped $3.39, or 16 percent, to $18.26.

Dell tumbled $2.19, or 9.9 percent, to $19.91 after it said aggressive price cuts in the personal computer market would cause the company to miss forecasts. The stock was cut to "hold" from "buy" by A.G. Edwards.

On the positive side, Microsoft Corp.'s profit fell, but still surpassed expectations, and investors sent its stock up $1.02, or 4.5 percent, to $23.87 on word of its $20 billion buyback. Sometime rival Google Inc. rose $2.99 to $390.11 after it again blew past Wall Street's expectations after more than doubling its second-quarter profits.

The Russell 2000 index of smaller companies was down 11.67, or 1.71 percent, to 671.94.

Overseas, Japan's Nikkei stock average fell 0.84 percent. In Europe, Britain's FTSE 100 closed down 0.89 percent, France's CAC-40 was lost 0.96 percent for the session, and Germany's DAX index slid 1.71 percent.

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The Dow Jones industrials ended the week up 129.03, or 1.2 percent, finishing at 10,868.38. The S&P 500 index gained 4.09, or 0.33 percent, to close at 1,240.29.

The Nasdaq dropped 16.96, or 0.83 percent, to end at 2,020.39.

The Russell 2000 index closed the week down 9.30, or 1.37 percent, at 671.94.

The Dow Jones Wilshire 5000 Composite Index — a free-float weighted index that measures 5,000 U.S. based companies — ended the week at 12,407.16, off 20.55 points from last week. A year ago the index was 12,337.25.