U.S. stocks rose Thursday, with the Dow hitting another record high, as strong earnings from Exxon Mobil Corp. (XOM) and health insurer Aetna Inc. (AET) outweighed concern that share prices may be too high after a recent run-up.

The Dow Jones industrial average was up 28.98 points, or 0.24 percent, to close at 12,163.66. The Standard & Poor's 500 Index was up 6.86 points, or 0.50 percent, at 1,389.08. The Nasdaq Composite Index was up 22.51 points, or 0.96 percent, at 2,379.10, a 5 1/2-year high.

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Earlier, the Dow rose as high as 12,167.02, an intraday record.

Setting the pace for Friday, shares of Microsoft Corp. (MSFT), the world's largest software maker, dipped to $28.29in composite trading after the closing bell. Microsoft reported a higher quarterly net profit, boosted by a strong performance at its database software division. In regular trading on Nasdaq, Microsoft closed at $28.35.

The Nasdaq Composite Index received one of its biggest lifts from Comcast Corp., the largest U.S. cable operator, which reported a stronger-than-expected increase in quarterly profit. Comcast shares rose 3.2 percent, or $1.24, to $40.00.

The Dow Jones industrial average has hit a new record high in 12 of the past 17 sessions and been on a gradual ascending path since mid-July, prompting some investors to ask whether companies' performances will continue to justify prices.

"Investors are beginning to buy stocks in sectors, such as energy, that were left behind somewhat during the recent rally," said Subodh Kumar, chief investment strategist at CIBC World Markets in Toronto. "Valuations in some groups may be stretched, but there are still gains to be made."

Exxon Mobil shares rose 0.9 percent, or 61 cents, to $71.62 and Aetna's stock jumped 7.4 percent, or $2.86, to $41.39 on the New York Stock Exchange. Quarterly results for both companies beat Wall Street expectations.

Property and casualty insurers rose, with shares of No. 1 U.S. insurer American International Group Inc. up 1.4 percent, or 95 cents, at $67.78, after St. Paul Travelers was the latest in the group to beat estimates on solid quarterly numbers. AIG was one of the Dow's biggest gainers and among the S&P 500's top advancers. St. Paul shares rose 4.3 percent, or $2.07, to $50.66.

Clear Channel Communications Inc. (CCU), the largest U.S. radio company, gained nearly 10 percent, or $3.13, to $35.48 on news that a group of private-equity firms were in advanced talks to buy the company.

Pressuring the Dow was Boeing Co. (BA), which shed 2.1 percent, or $1.72, to $79.14, a day after the jet plane manufacturer issued a disappointing forecast for 2007.

Volume was heavy on the NYSE, where about 1.74 billion shares changed hands, above last year's daily average of 1.61 billion. On the Nasdaq, about 2.39 billion shares were traded, above last year's daily average of 1.80 billion.

Gainers outnumbered decliners on both the Big Board and the Nasdaq by about 2 to 1.

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