The board of directors announced that Fiorina stepped down as chairman and chief executive, effective immediately.
Robert P. Wayman, HP's chief financial officer, has been named interim CEO. Patricia C. Dunn, an HP director since 1998, has been named non-executive chairman of the board.
"Carly Fiorina came to HP to revitalize and reinvigorate the company," Dunn said in a prepared statement. "She had a strategic vision and put in place a plan that has given HP the capabilities to compete and win. We thank Carly for her significant leadership over the past six years as we look forward to accelerating execution of the company's strategy."
Fiorina joined Hewlett-Packard in July 1999 as chief executive. She was named chairman one year later.
She repositioned the company, including its 2002 merger with Compaq Computer. It was one of the largest high-tech mergers in history.
Fiorina earned a bachelor's degree in medieval history and philosophy from Stanford University. She received an M.B.A. from the University of Maryland and an M.S. from M.I.T.'s Sloan School.
She worked for AT&T and Lucent Technologies (nyse: LU - news - people ) for 20 years before joining HP.
Hewlett-Packard plans to report first-quarter results after the market close Feb. 16. It expects results to be in line with analysts' consensus estimates of 37 cents per share.
HP shares rose as much as $2.12 to $22.26 from yesterday's close of $20.14. Later in the morning, they settled to a gain of about a dollar per share. Based on an average of 2.991 billion shares outstanding on a diluted basis for the fiscal fourth quarter ended Oct. 31, 2004, that gain of one dollar per share from Fiorina's resignation has added about $2.991 billion in market capitalization to the company.
Last month, HP's board of directors discussed shifting some day-to-day duties to other executives from Fiorina in an effort to boost the company's performance.
At the time, company insiders said Fiorina's job was not in question.
Fiorina is perhaps best known for heading HP's difficult $19 billion merger with Compaq Computer in 2002. Some analysts said it was difficult to mesh the different company cultures--HP sought a consensus before moving forward while Compaq quickly made decisions and acted on them.
Wall Street turned thumbs down on the deal, driving down shares of HP and Compaq. At one point, the $25 billion stock deal took nearly a $8 billion hit.
Many HP employees wrote letters to the editor of Forbes.com about the merger. One said, "Carly Fiorina has lost the people of HP. She is reviled, despised and unwelcome in the company. The vast majority of HP people wouldn't follow her to a new restaurant, much less through a gut-wrench merger."
HP was unable to regain the top spot in the Unix server market under Fiorina.
HP squandered its leadership and allowed Sun Microsystems (nasdaq: SUNW - news - people ) to leap ahead. HP decided to hold back development of its Unix chip platform, industry sources said, in an apparent effort to appease Intel (nasdaq: INTC - news - people ), its development partner in Itanium, a competing architecture.
Sun spent less than $100 million to buy the high-end UltraSPRAC from Cray Research in July 1996. Sun's investment turned into a multibillion dollar business. Fiorina tried to fix HP's Unix server business when she joined the company in July 1999.