Wall Street plunged in trading Friday — and the Dow Jones industrial average closed below the psychologically key 10,000 level — after investors reacted to disappointing profit forecasts from Microsoft and Amazon.com that topped off a week's worth of mixed earnings.

The Dow Jones industrial average tumbled 88.11 points, or 0.88 percent, to close at 9,962.22. The last time the Dow closed below 10,000 was May 24. The Nasdaq Composite Index lost 39.97 points, or 2.12 percent, to end at 1,849.09, while the broader Standard & Poor's 500 ended lower 10.64 points, or 0.97 percent, at 1,086.20.

For the week, the Dow and Nasdaq both fell 1.8 percent, while the S&P 500 was down 1.4 percent. It was the fourth straight down week for the Nasdaq, the fifth losing week for the Dow and the sixth for the S&P 500.

Friday's session capped a challenging week of mixed earnings and economic data that has pointed to what Federal Reserve Chairman Alan Greenspan (search) called a "soft spot" in the economic recovery.

"You take the economic data over the last few weeks, which has been disappointing, and now all these negative earnings outlooks, and then you add in all the worries about energy prices, terrorism, Iraq, the elections — there's a lot to worry about out there," said Michael Sheldon, chief market strategist at Spencer Clarke LLC. "It's going to take a while for these issues to be resolved, and I think we'll be stuck moving sideways to lower until then."

Without a strong catalyst to the upside, the odds are now clearly against any strong rallies in the market for the coming months based on historical trading patterns.

Microsoft Corp. (MSFT), the world's second-largest company by market value, prompted Friday's sell-off after it posted a quarterly profit in line with expectations after Thursday's bell, but guided its outlook for the year lower on expiring long-term corporate contracts and slowing investment income. The news from the world's largest software maker increased investor concerns that earnings growth is slowing across the board, making share valuations looked stretched.

The company said slower personal computer sales growth would also make it difficult to match its 14-percent revenue growth in fiscal 2004, since PC sales drive sales of its Windows operating system. Its stock slipped 97 cents to $28.03.

Amazon.com Inc. (AMZN) also added to investor woes after it posted quarterly profits that were a penny short of Wall Street's expectations and its forecast for the third quarter was also weaker than previously anticipated. Its shares plunged $5.84, or 12.75 percent, to $39.98 on the Nasdaq.

However, it wasn't just tech firms that weighed on investors. The Coca-Cola Co. (KO) slumped $3.80, or 7.76 percent, to $45.17 despite beating Wall Street expectations by a penny. The soft drink maker said its international businesses were coming under increasing competitive pressure.

In other corporate news, oilfield services company Halliburton Co. (HAL) fell 49 cents to $30.55 after it posted a loss for the quarter due to charges related to discontinued operations and asbestos-related litigation. Middle Eastern contracts pushed revenue higher, however, and the company beat estimates by a penny.

Xerox Corp.'s (XRX) recovery continued apace in the second quarter, with the printer and copier manufacturer beating analysts' estimates by 4 cents per share. Xerox was up 49 cents at $13.80.

Declining issues outnumbered advancers by about 2 to 1 on the New York Stock Exchange, where volume was very light.

The Russell 2000 index of smaller companies was down 7.30, or 1.3 percent, at 539.22.

Overseas, Japan's Nikkei stock average fell 0.9 percent. In afternoon trading, Britain's FTSE 100 closed up 0.5 percent, while France's CAC-40 dropped 0.2 percent for the session and Germany's DAX index fell 0.1 percent.

Reuters and The Associated Press contributed to this report.