By Benjamin Pimentel, MarketWatch SAN FRANCISCO (MarketWatch) -- The technology sector kicked off the week in the red, with shares of Microsoft Corp., Hewlett-Packard Co. and Intel Corp. highlighting the early Monday retreat. Shares of Research In Motion Ltd. (RIMM) were also down nearly 5% at $9.37 after Morgan Stanley downgraded the stock to underweight, or sell, saying "the only way RIM remains a viable entity is at a fraction of its current size, a transformation that erases much of its earnings power." Microsoft (MSFT) shed 2.5%, while H-P (HPQ) slid 2.1% and Intel gave up 2.6%, joining the three worst performers on the Dow Jones Industrial Average (DJI) . The Dow was down 164 points as worries about the European financial crisis and the expected U.S. Supreme Court ruling on the 2010 Affordable Care Act weighed on Wall Street. The Nasdaq Composite Index (DJI) shed 1.8% to 2,840, while the Philadelphia Semiconductor Index (SOX) was off 2.6%. Shares of Nvidia Corp. (NVDA) slid 1.5% despite getting an upgrade to buy from hold by Canaccord Genuity. Analyst Bobby Burleson cited the chip maker's strong position in the mobile market with its Tegra platform. Shares of SanDisk Corp. (SNDK) were trading flat, after briefly getting a lift from an upgrade to buy from Goldman Sachs. Analyst James Schneider cited an expected improvement in the NAND Flash memory market, saying in a note: "We now believe NAND suppliers are pushing out capacity expansion given current industry oversupply." Red Hat Inc.'s (RHT) shares fell 1.3%. Needham analyst Scott Zeller initiated coverage of the software company's stock with a buy rating, citing growing interest in the data center market for "open source alternatives as companies consider their architectures for 'data center refresh' and a move to cloud computing for public as well as private cloud buildouts." Modest gains came from the social media group. Shares of Yelp Inc. (YELP) gained 1.5%, while Zynga Inc. (ZNGA) added a fraction. But Facebook Inc. (FB) and LinkedIn Inc. (LNKD) were each down about 2%.