The Nasdaq composite index was up 23 points at one point during the day, but it closed down 26.52 at 3,290.25, while the Standard & Poor's 500 index inched up 0.45 to 1,374.62.
The Dow Jones industrial average rose about 80 points during the day with a 46.62 point gain at 10,238.80.
"There was something for everybody today," said Todd Clark, head of listed trading at WR Hambrecht. Bullish investors could feel optimistic that the markets retained much of Friday's sharp gains, he said, but bears could remain skeptical about the narrow trading breadth and low volume.
Winners and losers were even on the Nasdaq, which generated a modest volume of 1.78 billion shares. The New York Stock Exchange also generated a moderate volume of 999 million shares as one stock rose for every stock that fell.
Clark said he is concerned that the markets have not yet found a bottom. "I don't think you can rule out a retesting of the lows reached over the past few weeks."
Dick McCabe, chief market analyst at Merrill Lynch, also said past performance suggests that "at least a retest or moderate undercut of last week's low on the averages...is likely in coming weeks before an important bottom is in place."
Stock prices took a roller-coaster ride last week. Despite strong gains on Friday, when the Nasdaq jumped nearly 8 percent, the S&P finished the week down 4 percent, while the Dow lost 2 percent and the Nasdaq shaved 1 percent.
At the end of regular trading today, Intel fell $4.69, or about 12 percent, to $35.69 and was the most actively traded stock on the Nasdaq with a volume of nearly 92 million shares.
The shares slid after Salomon Smith Barney analyst Jonathan Joseph told investors in a report that the world's biggest chipmaker faces weaker demand at a time it's adding capacity.
"The much-hoped-for mid-October pickup in personal-computer demand has failed to materialize, which suggests to us Intel's guidance on its Tuesday afternoon conference call will be more cautious than most investors anticipate," Joseph wrote.
Intel also weighed on the Philadelphia semiconductor index, which fell 43.82, or nearly 6 percent, to 714.50. Chipmaker Micron Technology dropped $2.69 to $33.69, and Advanced Micro Devices slipped $1.50 to $20.38. Chip equipment company Applied Materials also fell $4.75 to $48.75, and Novellus lost $5.63, or about 14 percent, to $34.88.
Other large cap tech stocks took a hit. Microsoft fell $3.38 to $50.38; Cisco Systems slipped $1.56 to $54.50; and Oracle stumbled $1.06 to $34.56. Microsoft shares hit a new 52-week low of $49.56 compared with a high of $119.93 over the same period. Juniper Networks gained $14.50 to $243.
Shares of IBM and Sun Microsystems received a boost from some positive analyst comments. IBM gained $2.06 to $111.13, and Sun Microsystems climbed $3.56 to $114.56 after Merrill analyst Thomas Kraemer raised earnings forecasts for the companies on optimism that revenue growth is sustainable.
Citing the results of a Merrill Lynch-sponsored survey, Kraemer raised his third-quarter and annual earning estimates for IBM by 3 cents and raised his first-quarter estimate for Sun by 3 cents to 28 cents.
The CNET tech index lost 44.25 to close at 2,607.89. Losers edged out winners, with 67 of the 97 stocks in the index falling, 35 rising and two remaining unchanged.
Of the 18 sectors tracked by CNET Investor, computer memory storage and semiconductor equipment companies posted the sharpest drops, falling 5 percent. Server hardware makers were the day's largest gainers, climbing 3 percent.
Shares of e-tailer Amazon.com also took a hit, falling $4.13, or 14 percent, to $24.31 while eBay gained $3.75 to $59.63.
Among members of the CNET tech index, Qualcomm posted strong gains.
Shares of Qualcomm rose $7.06 to $77. The company announced that it has joined China Unicom and an equipment maker to produce a cellular phone based on Qualcomm's wireless standard.
Investors were not as enthusiastic about shares of Xerox, which fell $2.69, or nearly 26 percent, to $7.75. In early trading, the shares set an intraday 52-week low of $6.75 compared with a high of $43.31.
The Nihon Keizai newspaper reported yesterday that the copier maker has no concrete plans to sell shares in Fuji Xerox, its unit in Japan, citing Fuji Xerox chairman Yotaro Kobayashi.
The comment came after Xerox, seeking to temper concerns that it may not be able to fund its daily operations, said Friday it has adequate access to financing.