Stocks regained on Friday a chunk of the ground they lost Thursday, but volume shows that investors were more eager to unload than they were to buy back. The Nasdaq rose 1.2%, the S&P 500 recouped 0.7% and the Dow Jones industrial average added 0.6%. Each index sliced below its 50-day moving average Thursday and was unable to regain it Friday. Volume fell 16% on both the Nasdaq and the NYSE, according to preliminary data. For the week, the Nasdaq