The survey by Gartner found China's Lenovo edging past Hewlett-Packard as the world's largest vendor, reclaiming the top spot it had captured briefly last year.
The preliminary figures showed a worldwide drop of 10.9 percent in the second quarter compared with the same period a year ago, with PC shipments falling to 76 million units.
"We are seeing the PC market reduction directly tied to the shrinking installed base of PCs, as inexpensive tablets displace the low-end machines used primarily for consumption in mature and developed markets," said Mikako Kitagawa, analyst at Gartner.
"In emerging markets, inexpensive tablets have become the first computing device for many people, who, at best, are deferring the purchase of a PC. This is also accounting for the collapse of the mini notebook market."
Gartner's survey showed Lenovo taking a 16.7 percent global market share with shipments of 12.67 million units, just ahead of HP's 12.4 million and 16.3 percent share. Both firms saw sales declines, but Lenovo's was limited to 0.6 percent while HP sales fell 4.8 percent.
Dell was the number three vendor, with sales of 8.9 million and a market share of 11.8 percent.
Number four vendor Acer experienced a drop of 35 percent, and fifth-place Asus showed a 20.5 percent drop as the two Taiwan-based firms decided to exit the mini-notebook market.
The PC market has been struggling amid a shift to tablets, and got little help from the new Windows 8 operated system introduced by Microsoft last year.
"While Windows 8 has been blamed by some as the reason for the PC market's decline, we believe this is unfounded as it does not explain the sustained decline in PC shipments, nor does it explain Apple's market performance," Kitagawa said.
Apple was not among the top five global vendors, but was third in the US market with a 4.3 percent drop in sales in the past quarter, Gartner said.
Overall US sales totaled 15 million units in the second quarter, a 1.4 percent decline from a year earlier, and the figure was 8.5 percent higher than the first quarter.
Kitagawa said the US market showed resilience because of "solid growth in the professional market," with some replacements of corporate computers.
In the region including Europe, the Middle East and Africa, PC sales saw a 16.8 percent year-over-year drop, Gartner said. In Asia, the drop was 11.5 percent.
A separate survey by research firm IDC showed a similar picture, estimating the decline at 11.4 percent and 75.6 million units.
But IDC said the decline was not as bad as its earlier forecasts.
"We are still looking for some improvement in growth during the second half of the year," said Jay Chou, an IDC analyst.
"While efforts by the PC ecosystem to bring down price points and embrace touch computing should make PCs more attractive, a lot still needs to be done in launching attractive products and addressing competition from devices like tablets."
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