WASHINGTON — Hewlett-Packard Co. said Thursday it is cooperating with U.S. and German authorities investigating allegations that three company executives used bribes to win a contract to sell computer gear to the Russian prosecutors' office. German prosecutors have been looking into whether the executives, plus at least six accomplices who did not work for the company, paid bribes totaling 8 million euros (about $10.3 million) to win a 35 million-euro contract to supply computers, software and hardware to the Russians.