Forget what Apple (Nasdaq: AAPL) says. The iPad is neither cute nor fun. It's a cold-blooded killer of PC market share.

According to data from researchers at Gartner and IDC, the iPad demolished Acer's U.S. share of the PC market in the fourth quarter, as consumers began to increasingly regard tablets as viable alternatives to lightweight netbooks.

"These devices do not replace primary PCs, but they are viewed as good enough devices for these who want to have a second and third connected device for content consumption usage," said Gartner analyst Mikako Kitagawa in a press release. "Mini-notebook shipments were hit the most by the success of media tablets."

Here's a closer look at Gartner's roundup of the victims, which included leading PC makers Dell (Nasdaq: DELL) and Hewlett-Packard (NYSE: HPQ):

Prelminary U.S. PC vendor unit shipment estimates

Company

Q4 2010 Shipments

Q4 2010 Market Share (%)

Q4 2009 Shipments

Q4 2009  Market Share (%)

Year-Over-Year Growth (%)

HP 17,581,525 18.8 17,786,986 19.6 -1.2
Acer Group 11,852,617 12.7 12,075,091 13.3 -1.8
Dell 10,801,225 11.6 10,395,288 11.5 3.9
Lenovo 9,481,565 10.1 7,809,357 8.6 21.4
Toshiba 5,346,700 5.7 4,768,306 5.3 12.1
Others 38,416,677 41.1 37,816,171 41.7 1.6
Total 93,480,310 100.0 90,651,199 100.0 3.1

Data includes desk-based PCs, mobile PCs, and mini-notebooks, but not media tablets such as the iPad.

Source: Gartner (January 2011).

The story gets more interesting if you include the iPad. Wall Street predicts that Apple sold 6 million tablets during the holiday quarter. Add that to Gartner's Mac sales projection, and you've suddenly got a PC powerhouse accounting for 31.3% of the market.

Unfair math, you say? Go tell Microsoft (Nasdaq: MSFT) CEO Steve Ballmer. He's the one who called the iPad a PC at last June's D8 tech industry conference.

The lines are blurring between what is and isn't a PC -- which surely favors Apple. Is there really anyone left who doubts that the company will blow away estimates when it reports earnings next week? Please let us know where you stand by voting in the poll below, then leave a comment to explain your thinking.

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Fool contributor Tim Beyers is a member of the Rule Breakers stock-picking team. He had stock and options positions in Apple at the time of publication. Check out Tim's portfolio holdings and Foolish writings, or connect with him on Twitter as @milehighfool. You can also get his insights delivered directly to your RSS reader. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool owns shares of Apple and Microsoft. The Fool is also on Twitter as @TheMotleyFool. Its disclosure policy would appreciate a little sunshine over here. Thanks.