I admit it -- I thought the PC market was about done growing by double digits. Shows you how much I know.

Yesterday, researchers IDC and Gartner (NYSE:IT) both reported substantial gains in global computer shipments during the second quarter. IDC pegged the year-over-year gains at 16.6%, while Gartner came in at 14.8%. Most impressive is that the results were well ahead of expectations. IDC, for example, had predicted only 12.3% growth for the quarter at the end of May, according to Reuters.

Both firms attributed the growth to consumer interest in notebook computers and very low-cost PCs. They also said businesses continued upgrading older systems. International expansion, too, was a major factor in the results. Indeed, IDC said Europe, the Middle East, and Africa saw a 20% uptick and that demand in the Asia-Pacific region improved. Growth in the U.S. picked up, as well.

Not surprisingly, the big winners were Apple (NASDAQ:AAPL) and Motley Fool Stock Advisor pick Dell (NASDAQ:DELL). Apple boosted global shipments by 37% and expanded its U.S. market share to 4.5%, according to IDC -- hardly surprising after reporting a blowout quarter last week. Dell increased global unit shipments by 24% and increased its worldwide market share to 19.3%, improving 1.1% over a year ago. Lenovo, which bought IBM's (NYSE:IBM) PC business, and Gateway (NYSE:GTW) also expanded market share. Second-place Hewlett-Packard (NYSE:HPQ) grew global sales 16% while maintaining its 15.6% global market share.

But can the expansion continue? At the moment, it certainly seems so. With 6.5 billion people on this little planet of ours (give or take a few million), the majority of whom reside in developing parts of the world, there's a good chance many of them don't yet have personal computers. And those who do are going mobile, or perhaps treating their existing machines as consumables to be replaced as often as (or even more often than) a vehicle. Which of course means there could be plenty of headroom left in the global market, which would in turn power big gains for at least one of the stocks in this sector.

Wall Street's so-called experts would probably say Apple or Dell will get the lion's share, and this is one time I'd tend to agree with them.

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Fool contributor Tim Beyers will stick with his Mac PowerBook, thank you very much. Tim didn't own shares in any of the companies mentioned in this story at the time of publication. You can find out exactly what's in his portfolio by checking his Fool profile here. The Motley Fool has an ironclad disclosure policy.