Carly Fiorina, whose controversial six years as head of Hewlett-Packard Co. was highlighted by the company's purchase of Compaq Computer Corp. in 2002, resigned Wednesday as chairman and CEO.

HP Chief Financial Officer Robert Wayman will step in as interim CEO, while Patricia Dunn, a member of the board of directors since 1998, will take over as non-executive chairman, HP said in a statement released Wednesday morning.

Both appointments take effect immediately.

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"Carly Fiorina came to HP to revitalize and reinvigorate the company," Dunn said in a 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 said that the resignation was the result of disagreements on HP's future.

"While I regret the board and I have differences about how to execute HP's strategy, I respect their decision," she said in a statement. "HP is a great company and I wish all the people of HP much success in the future."

Fiorina's resignation follows months of criticism from inside the industry and inconsistent results. In the third quarter last year, HP stunned analysts when it announced that its Enterprise Storage and Servers group lost $208 million, due to problems with order fulfillment and a migration of its order management operations.

For more on the Enterprise Storage and Servers group's loss and the shakeup that followed, click here.

Over the past year, Fiorina also has consolidated HP's businesses, last year combining its enterprise systems group with its services unit, and earlier this year folding its PC business into the highly profitable Imaging and Printing Group, which generates almost three quarters of HP's revenues.

However, it was the company's purchase of Compaq for about $19 billion that Fiorina will be remembered for. That purchase followed a bitter proxy battle with HP heir Walter Hewlett, who worried that bringing Compaq into the fold would hurt the company's profitable businesses and force it to rely too heavily on a shaky PC business. The board of directors backed Fiorina's decision to pursue the purchase.

The pressure had been mounting on Fiorina, 50, in recent weeks. Reports circulated last month that the board of directors was considering pulling back on some of Fiorina's duties. HP spokespeople denied that any changes were under way.

Fiorina came to HP from Lucent Technologies Inc.

In a statement, the board of directors said it will immediately start a search for Fiorina's replacement.

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