SAN FRANCISCO (MarketWatch) -- Big gains from Microsoft Corp. MSFT, -1.24% , Amazon.com Inc. AMZN, -1.78% , as well as online social gaming company Zynga Inc. ZNGA, +0.95% gave some muscle to the tech sector in early trading Friday. Microsoft and Amazon each rose almost 7%, and Zynga's stock was up by nearly 12% on upbeat reaction to all three companies' late-Thursday earnings reports. With those companies in the lead, the Nasdaq Composite Index COMP, -1.07% rose by 22 points to 3,951.