Stocks defended most of their early gains near midday Friday, as the major indexes stayed on course to book losses for the week. The Nasdaq, S&P 500 and the Dow Jones industrial average were all up 0.4%. Volume for the stock market today was steady and thin, down 22% on both the Nasdaq and the NYSE compared to Thursday trade. Hewlett-Packard (HPQ) led the S&P 500 with a 10% gain after a solid fiscal first-quarter report. Aruba Networks (ARUN)