NEW YORK (CNNMoney) -- It was a miserable Christmas for personal computers, after holiday discounts and new ultra-thin laptops failed to win consumers over.
Technology consultancy Gartner said U.S. PC shipments fell 6% last quarter from a year earlier, as tablets and smartphones continued to capture more of consumers' interest.
One device category that many predict will save the PC -- the super-thin ultrabook laptops -- were quietly introduced into the market during the holiday season and barely made an impact on sales.
Instead, the PCs that saw the most sales growth were ones the most unlike mobile devices: all-in-one PCs with large, high-definition screens, Gartner said.
"Ultrabooks didn't seem to draw consumers' attention," said Mikako Kitagawa, principal analyst at Gartner. "Consumers had very little understanding and awareness of ultrabooks, and only a small group of consumers was willing to pay the price premium for such models."
But ultrabooks had a strong introduction this week at the Consumer Electronics Show in Las Vegas. Kitagawa said as awareness rises and prices fall below the $1,000 level most are offered at now, the super-thin devices could ultimately boost PC sales this year.
Sales of ultrabooks are forecast to boom over the next few years in the same way that netbooks took off in 2007 before the iPad debuted in 2009. Fewer than 1 million ultrabooks were sold last year, making up just 2% of all notebook sales, according to estimates by IHS iSuppli, a tech analysis firm. But next year, the ultra-thin notebooks will rise to 13% of all laptop sales, iSuppli forecasts.
Meanwhile, the PC is struggling to gain consumers' interest in a world where smartphones and tablets can do many of the day-to-day computing tasks that once required a personal computer. Apple (AAPL, Fortune 500) was the only major PC vendor to sell more computers in the United States during the fourth quarter of 2011 than a year earlier.
Shipments of Macs rose by nearly 21% last quarter. Meanwhile shipments of computers made by No. 1 PC-maker Hewlett-Packard (HPQ, Fortune 500) fell 26%. Shipments fell 4.5% at No. 2 Dell (DELL, Fortune 500), 2% at No. 4 Toshiba and more than 11% at No. 5 Acer. Apple is the third-largest PC maker in the United States.
PC shipments measure sales to vendors like Best Buy (BBY, Fortune 500) and Staples (SPLS, Fortune 500), not to end users. But shipments and end-user sales tend to be similar, since vendors order PCs based on buyers' demand for them.
U.S. shipments totaled 68.7 million in 2011, down 4.2% from 71.7 million in 2010.
The situation is only slightly better globally, where PC sales fell 1.4% during the quarter. For the year, global PC shipments were flat with 2010 levels -- well below the 4% increase that Gartner had predicted in a revised forecast issued in September. Gartner had initially forecast a 10.5% increase for 2011 and continually revised that lower during the year, as consumer sales sank sharply in the United States and Western Europe. Businesses and consumers in regions with emerging economies like Latin America and Asia bought enough PCs to close the worldwide gap.
For 2012, Gartner currently predicts worldwide PC shipments will rise 10.5%, but a revised forecast is due out in coming months.
Making matters worse, the impact of floods in Thailand hasn't yet been fully felt. The floods have sharply reduced the world's hard drive supply, but stockpiles were large enough for the shortage to have a limited impact on fourth-quarter PC shipments and prices, Gartner said.
But Gartner analysts believe that a "major impact" will still be felt, materializing in the first half of the year -- and potentially throughout 2012. A resulting laptop shortage and potential price increases will weigh on PC shipments this year.
All of this serves as an ominous sign for PC-reliant companies like Microsoft (MSFT, Fortune 500) and Intel (INTC, Fortune 500), which are scheduled to report their financial results in a week.
So far, the companies have both been able to weather the storm, but both are making large pushes into the mobile arena to capitalize on consumers' trend away from PCs and toward smaller, mobile devices. 
