An Illinois man who sent threatening letters demanding $5 million from Bill Gates planned to use the money to open a nightclub, prosecutors said.

Adam Quinn Pletcher, from the Chicago suburb of Long Grove, went on trial Monday in federal court on four counts of mail extortion. He could be sentenced to 20 years in prison and fined $250,000 on each count.He is accused of sending four letters to the Microsoft Corp. chairman threatening to kill him, his wife or another Microsoft executive.

Pletcher has pleaded not guilty, and his attorney said Monday that the 22-year-old was merely "playing out an imaginative scenario" by sending Gates the letters.

Prosecutors said Monday that they have threatening letters, a signed confession, applications for offshore bank accounts and a detailed proposal for a nightclub as evidence against Pletcher.

In one letter read in court by prosecutor Bill Redkey, Pletcher wrote that he was "a 34-year-old ex-Ranger . . . an assassin."

Pletcher's mother, Dana, said outside court that her son does not deserve to go to jail.

"Adam makes the world a better place - except for this," she said. "He's not a threat to society."

Forbes magazine estimated last year that Gates' net worth is nearly $40 billion, making him the world's richest man, excluding royalty.