NEW YORK, JULY 26 -- The Dow Jones industrial average closed down 10 points today after recovering only partially from a 30-point spill at midafternoon.

Computerized selling programs were largely driving the market, but traders also said that market psychology was sour from the day's opening because of a bundle of new, disappointing earnings reports.

Particularly notable earnings-related losses befell Compaq Computer, Data General and Raychem and Imperial Chemical Industries.

A wild midday plunge in Microsoft's over-the-counter shares, despite Wednesday's glowing fourth-fiscal-quarter earnings report, further dampened market sentiment. The 8-point slide to 66 was premised on perceptions from an analysts' meeting of a probable squeeze on profit margins in 1991. Microsoft rebounded to lose 2 3/4 at 68 3/4 in very heavy volume of 4.2 million shares.

Neither did a sharp loss in Eli Lilly help the bullish camp. Lilly tumbled on news that widows of three men killed in September 1989 at a Kentucky printing firm filed a wrongful-death suit against Lilly, charging that the man who was responsible for the shootings was at the time of the incident undergoing treatment with Prozac, a drug of the company's.

Philip Morris Inc. extended early losses on new reports that its merger with Switzerland's Jacobs Suchard may be undermined by a Suchard shareholders' revolt, as well as on news that it has lost smoking-liability litigation in New Jersey, posing the risk of snowballing lawsuits. It lost 1 3/4 to 47 1/4.

At the close, the Dow stood at 2920.79, down 10.15, while declines edged advances on the Big Board on moderate volume of 155 million shares.

Compaq closed off 1 1/2 at 57 7/8, Data General finished off 1 at 7 7/8 and Raychem ended down 1 7/8 at 26 3/8.

Two issues in particular overcame the session's generally gloomy tone. Du Pont rose 1 1/2 to 40 7/8 while Merck gained 7/8 to 89 7/8 on news from late Wednesday that they will form a joint venture for marketing and researching drugs.

The Dow transports inched up 0.55 to 1142.16, while the utilities gained 0.51 to 203.16. The Standard & Poor's 500 was down 1.18 at 355.91, the NYSE Composite down 0.55 at 194.55, the Amex Market Value down 0.62 at 356.33 and the Nasdaq Composite down 0.02 at 445.43.