Dell Inc's quarterly earnings and margins blew past Wall Street expectations as component costs slid and corporations replaced aging technology, propelling its shares 6 percent higher.

Its forecast for a 5 to 9 percent rise in current fiscal-year revenue also modestly surpassed Street targets.

Dell executives expressed confidence that the company could sustain the boost in profitability, but some analysts questioned that premise. Dell posted a gross margin of 21.5 percent -- about 15 percent above the average forecast -- aided in part by falling prices of items like memory chips and LCD screens.

Shares of Round Rock, Texas-based Dell leapt nearly 6 percent to $14.70 after hours, following a brief trading suspension, from a regular Nasdaq close of $13.91. It had spiked briefly as much as 8 percent after the news.

Shares of larger rival Hewlett-Packard Co, which would also benefit from lower input costs and better corporate spending, gained more than 1 percent to $48.54 after hours.

In Asia trading too, shares of PC makers rose, though the gains were partly attributed to the weaker Asian currencies. Japan's Toshiba Corp and Taiwan's Acer Inc climbed over 2 percent each.

Quanta Computer Inc, which supplies about 12 percent of Dell's total PC shipments, surged as much as 4.5 percent.

Dell's positive outlook is a plus for its OEM suppliers' businesses, but their share price will still be weighed on by rising costs and thinning margins, said Taiwan International Securities' assistant vice president Andrew Deng.

Dell's servers and networking revenue climbed 16 percent, while commercial personal computer revenue rose 10 percent, as businesses spent to upgrade outdated hardware.

There's still a majority of our customers who have not begun the corporate refresh, or who have started and still have a long way to go, Chief Financial Officer Brian Gladden said in an interview.

Although Gladden said he expects component costs to remain favorable through the first half of the new year, he downplayed input cost declines as the central factor in Dell's improved profitability. He stressed supply chain improvements and disciplined pricing. Dell's quarterly operating income was its highest in 5 years.

But many analysts still need convincing that Dell's turnaround effort is bearing fruit.

I still don't think in the long term they can sustain gross margins based on lower input costs because that will get competed away, said Michael Holt, an analyst at Morningstar.

Dell still pulls in most of its revenue from selling PCs. It has benefited from a surge in spending as businesses of all sizes spend again on equipment after two years of recession.

Dell is waging an uphill battle to diversify its revenue base: it wants to become a larger player in the data center equipment market, a provider of IT services, and gain a toehold in the fast-growing mobile space with tablets and smartphones.

But it faces stiff competition in those markets from the likes of International Business Machines Corp, HP and Apple Inc

The company said it expects more acquisitions in areas like storage servers and services to come.

We have made a steady number of acquisitions last quarter and we have every intention of continuing on that rhythm, Paul-Henri Ferrand, Dell's chief marketing officer of global consumer and SMB, told a telephone conference for Asian media.

The latest purchase by Dell was of data storage company Compellent Technologies Inc in December for about $960 million.

Investors have remained on the sidelines as Dell's turnaround plan proceeds in fits and starts. Analysts say they are still looking for the company to prove it can sustain higher levels of profitability.

HOW SUSTAINABLE?

Dell's non-GAAP gross margin came in well ahead of analysts' average estimate of 18.6 percent. Revenue rose 5 percent to $15.7 billion, matching Wall Street's target.

Operating margin rose across all four Dell units, including its consumer business, which had been a drag on profits.

Revenues were a little bit less than expected but they performed well on the margin side. Our question is -- how sustainable is this going forward? asked Brian Marshall, an analyst at Gleacher & Co.

For fiscal 2012, Dell expects revenue growth of 5 to 9 percent, translating into revenue of $64 billion to $67 billion, mostly higher than the average forecast for $64.4 billion according to Thomson Reuters I/B/E/S.

The No. 2 PC maker on Tuesday reported a net profit of $927 million, or 48 cents a share, in the fiscal fourth quarter ended January 28, up from $334 million, or 17 cents a share, a year ago. Excluding items, Dell earned 53 cents a share, beating the average estimate of 37 cents a share, according to Thomson Reuters I/B/E/S.

It sees non-GAAP operating income growth of 6 to 12 percent for fiscal 2012.

Although Dell has made plenty of noise in smartphone and tablet markets, its products have not been well-received, and it will have to work hard to set itself apart from rivals.

Gladden said the mobile business is currently immaterial to Dell and that he does not expect to see it contribute to the company for a couple of years.

(Additional reporting by Clare Jim in Taipei and Noel Randewich in San Francisco; Writing by Edwin Chan; Editing by Richard Chang and Muralikumar Anantharaman)

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