By Kasper Jade and Katie Marsal

Published: 11:45 AM EST

The popularity of Apple Computer's iPod digital music players is helping it sell more Macs, but so far it hasn't been enough to spark a rise in the company's share of the personal computer market.

According to research firm Gartner, worldwide PC shipments totaled 57 million units in the first quarter of 2006, representing a 13.1 percent increase over the same period last year. But in that time, Apple's share of the worldwide market slipped from 2.2 percent to a mere 2.0 percent, the firm's data shows.

Similarly, Apple's share of the personal computer market in the United States also remains relatively flat at 3.6 percent. Although this figure is down from 3.8 percent in the first quarter of 2005, Gartner's data indicates that Apple gained one tenth of a percent in share over the fourth quarter of 2005.

To Apple's credit, this uptick in U.S. PC market share was achieved during a quarter when most prospective Mac buyers were prolonging their computer purchases in favor new Intel-based models that had yet to come to market. This suggests the company could begin to realize some share gains in the latter half of the year, once all of its PC offerings are readily available with Intel processors.

Meanwhile, Apple rival Dell was able to maintain its No. 1 position in worldwide PC shipments during the first quarter with a 16.5 percent share. However, the company's shipment increase of 10 percent year-over-year marked its weakest performance since the third quarter of 2001, according to Gartner.

Taking advantage of Dell's weakness, Hewlett-Packard increased shipments by over 22 percent and significantly narrowed the gap between it and Dell with a 14.9 percent market share. Lenovo, Acer and Fujitsu Siemens rounded out the top five vendors, each with significantly less share than frontrunners Dell and HP.

In the U.S., Dell remained the clear leader in PC shipments with an 11.3 percentage point market share lead over HP. However, shipments were almost flat compared to a year ago and it's the first time that the company has exhibited growth below the U.S. market average, Gartner said.

According to the firm's data, overall PC shipments in the U.S. during the first quarter of 2006 rose 7.4 percent to 16.4 million units.