SAN FRANCISCO -- Worldwide PC sales increased at a healthy though slightly slower-than-expected pace in the fourth quarter, according to a new report. And the market will see further cooling in the coming years, the industry research firm IDC predicted on Wednesday. "Rising concerns about economic growth are likely to reduce expectations further, although we're still likely to see double-digit growth through 2008 and probably 2009," said IDC analyst Loren Loverde. IDC said PC shipments in the last three months of 2007 were up 15.5% year over year, thanks to strong demand for notebook PCs and low prices. The firm had said in December that it expected fourth-quarter PC sales to increase by 16.7%. Gartner, another industry research firm, pegged fourth-quarter PC growth at 13.1% on Wednesday. The reports come as Wall Street frets that a souring economic environment will pinch PC sales. On Tuesday, Intel ( INTC), the world's No. 1 maker of PC microprocessors, delivered below-seasonal sales guidance for the current quarter. The chipmaker's shares subsequently sank more than 11% despite comments by CEO Paul Otellini that business conditions remained healthy. According to Gartner, the U.S. PC market grew faster than expected in the fourth quarter, with shipments up 7.2% year over year. As usual in recent years, the most significant growth came from overseas markets such as the Asia/Pacific region and Latin America, where PC shipments increased 18.3% and 24.5% respectively. According to Gartner analyst Mikako Kitagawa, however, the growth rate in the Asia/Pacific region as well as in the EMEA, or Europe, Middle East and Africa region, were both slightly weaker than expected in the fourth quarter. Both Gartner and IDC crowned Hewlett-Packard ( HPQ) the world's No. 1 PC maker, and reported that the company pulled ahead of the pack, grabbing a 19% share of the PC market and growing its unit shipments 23% year over year. Dell ( DELL), which has focused on revitalizing its business in recent months, grew its PC shipments 17% in the fourth quarter and actually increased its market share to 14.5% of the PC market.