(Reuters) - Shares of Hewlett-Packard Co fell more than 7 percent Thursday, after the world's No. 1 computer maker posted a sharp decline in quarterly earnings and warned it would take several years to turn around its sprawling businesses.

Chief Executive Meg Whitman, who took over the top job in September after the company fired Leo Apothekar, requested investors to keep their patience and said a turnaround the size the company was efforting took considerable time.

J.P. Morgan Securities, however, said secular, macro and company-related risk may delay an appreciable turnaround.

RBC Capital said investors may look past the choppy revenue performance, given the temporary difficulty in procuring hard-disk drives, but added that it expects problems to continue into the second quarter.

On Wednesday, HP, which has been trying to pick itself up from the mess the company found itself last year, reported a decline in sales in three of its key units: personal computers, printers and enterprise equipment.

Revenue shortfall in PCs and significant quarter-on-quarter margin deterioration in every business raise questions about the competitiveness, cost structure and secular pressures in HP's business segments, Morgan Stanley said in a note to analysts.

Wall Street analysts fear that the multiple pressures that weighed on margins -- including yen strength, competitive hardware pricing and the ongoing HP Services restructuring -- are more than one-quarter issues, and could continue into coming quarters.

Earlier this week, Dell Inc, the world's No. 3 personal computer maker, also posted fiscal fourth-quarter earnings below analysts' expectations and forecast fiscal first-quarter revenue below estimates, stoking fears the PC industry has not fully emerged from its downturn.

While Dell did not have a particularly good January earnings call and in our opinion left a great deal of ambiguity in terms of the forces that impacted the January quarter, we believe HP's report, by comparison, was worse, said BMO Capital Markets' analyst Keith Bachman.

Bachman cut his price target on HP's stock to $33 from $35.

Of the 34 analysts covering HP, 18 rate it at hold, five at sell, six at strong buy, and five at buy, with a mean price target of $30.40, according to Thomson Reuters' StarMine data.

Shares of HP fell to $26.85 in Thursday morning trade. The stock has lost over 40 percent of its value since its 2011 high of $49.38.