Acer chief executive Gianfranco Lanci has resigned, following disagreements with the board over the future direction of the world's third-largest computer maker, which recently reported a dim outlook on PC revenue.

The Taiwanese company said Thursday that Lanci's resignation was effective immediately, and board chairman J.T. Wang would be acting CEO until a permanent replacement is found.

Lanci left the company less than a week after Acer reported that first-quarter PC revenue would fall short of expectations, due to weak sales in Western Europe and the United States. The company said revenue was about 10% less than in the fourth quarter of last year. In addition, Acer said PC shipments in the second quarter would be flat over the first quarter.

The weak outlook sent Acer stock plummeting, with the company losing more than $1 billion in market value in four days, the Reuters news agency reported.

Acer said Lanci and a majority of the board held different views on the company's future, and the parties could not agree, despite several months of discussion. "They placed different levels of importance on scale, growth, customer value creation, brand position enhancement, and on resource allocation and methods of implementation," the company said of the discussions.

Going forward, the PC would remain the core of Acer's business and the company would continue expanding its commercial computer business, Wang said in a statement. "In addition, we are stepping into the new mobile device market, where we will invest cautiously and aim to become one of the leading players."

In February, Acer announced plans to start selling later this year storage and servers in the United States for the first time. The company's initial offering would include a total of 16 tower, rack, blade, and rack multi-node servers. The systems would be based on Intel Xeon or Advanced Micro Devices' Opteron processors. Acer planned to resell Hitachi storage products.

Acer rode high in 2008 and 2009 on the popularity of netbooks, inexpensive mini-laptops that fit well in the company's strengths as a maker of low-priced consumer PCs. That netbook market waned considerably last year with Apple's introduction of the iPad tablet. The iPad has led to a wave of competing tablets from other vendors, all of which have cannibalized netbook sales, analysts say.

Acer introduced its Iconia Tab in February and said it would release more models in the second quarter. Whether these systems can get the company's sales back on track in a fiercely competitive market remains to be seen. Wang acknowledged that Acer would need "a period of time for adjustment."

IDC in January rated Acer as the world's third-largest computer maker, in terms of shipments, following HP and Dell.

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