HOUSTON - A prime defendant in Enron Corp.'s criminal trial has struck a deal with prosecutors and agreed to testify against the fallen energy giant's two top executives, according to a person familiar with the negotiations. [Estimates are at $1 Billion to Disassemble Former Energy Brokerage Enron, One of RNC's Largest Contributor's Who Wined and Dined Bush Campaign While Screwing Investors and Employees]