Gartner has just released new research showing that worldwide PC shipments totaled 90.3 million units in the fourth quarter of 2012, a 4.9 percent decline from the fourth quarter of 2011, caused mainly by tablets.

Gartner added that people feel much less impetus to replace their PCs if they have tablets they can use for basic functions such as reading the news and watching videos.

Gartner said the launch of Microsoft’s (MSFT) Windows 8 did not have a significant impact on PC shipments in the fourth quarter, although the firm expects that Windows 8 PC sales will improve as OEMs release top-tier touch screen computers throughout 2013.

Gartner said that HP (HPQ) retained its top spot in the PC market with a 15.5% share despite seeing its overall sales drop by 0.5% year-over-year. Lenovo came in second with a 13.6% share and was the only major PC vendor to see its total sales significantly grow from the previous year. Dell (DELL) saw its PC sales shrink by 20.9% year-over-year while Acer’s (2353) sales declined by more than 11%.