HOUSTON — Two former Enron executives received sharply reduced sentences yesterday after cooperating with prosecutors to help convict the architects of the biggest scandal in U.S. corporate history .

Michael Kopper, once the top lieutenant to former Enron Chief Financial Officer Andrew Fastow, was sentenced to three years and one month in prison. An hour later, Mark Koenig, the company's former investor relations chief, received 18 months.

The men were also fined $50,000 that will go to victims of Enron's collapse, and each will be on probation for two years after release.

Both men will remain free on bond until they have to report to prison, a process that usually takes four to six weeks.

Prosecutors had asked U.S. District Judge Ewing Werlein Jr. to cut the potential sentences because of their help. Kopper, 41, faced up to 15 years in prison after pleading guilty in 2002 to money laundering and conspiracy to commit wire fraud.

Koenig, 51, who helped present the company's false financial reports to investors, pleaded guilty in August 2004 to one count of aiding and abetting securities fraud, which carries up to 10 years in prison.

"I want to apologize to all the people who have been harmed by the Enron affair," Kopper said before he was sentenced. "Families and employees suffered not just monetary failure but reputational failure. I am very deeply sorry for having participated in causing that."

Koenig also apologized.

"I didn't make the right choices in my last year at Enron. I am profoundly sorry for that," said Koenig, whose wife and sons attended the sentencing.

Kopper's sentencing hearing was packed with family and friends, including his parents and his domestic partner.

Kopper's attorney, David Howard, said his client's charity and community work since his arrest is proof he is a changed man. "He is no longer that guy from Enron," Howard said.

"The sentence is not imposed for the good things you've done the past few years," Werlein told Kopper.

Kopper, 41, was the first former Enron executive to plead guilty to charges stemming from the company's collapse. He led federal prosecutors to Fastow, who in turn led them to Enron founder Kenneth Lay and former CEO Jeffrey Skilling.

Fastow just began serving six years in a federal prison in Louisiana, while Skilling will begin serving a sentence of more than 24 years next month in Minnesota. Lay, convicted of conspiracy, fraud and other charges, died in July from heart disease.

Earlier this week, Richard Causey, the company's former chief accounting officer, was sentenced to 5 1/2 years for his role in the company's collapse.

Prosecutors said that from May 1997 through September 2001, Kopper took advantage of off-balance-sheet partnerships and accounting methods to funnel millions of dollars to himself, Fastow and others at the expense of the company and its shareholders.

Howard said Kopper now lives a modest lifestyle after surrendering nearly $12 million in ill-gotten gains as part of his plea agreement.

Koenig's attorney, Philip Inglima, said his client has taken responsibility for what he did at Enron. "He is not a man who has sought to victimize others, but he realizes how his conduct" did that, Inglima said.