Acer has shown substantial growth over the past couple years, acquiring several PC makers and delivering competitive products as it strives to take HP's number one crown. Last December, market researcher iSuppli reported that in Q3 2009 the company actually moved one step closer to this goal by overtaking Dell's quarterly shipments for the very first time. Now the numbers for the whole year are in, and after repeating the feat in Q4, it seems even HP better take a look over its shoulder as Acer is coming up fast from behind.

Dell managed to hold on to the second-place spot by a mere 0.2% margin in 2009, but it was also the only top-five vendor to see shipments decline. The company moved 39.9 million PCs, a drop of 9.9% from 2008 that was good enough for a 12.9% share of the market. HP managed to extend its lead by taking an 18.9% market share. Meanwhile, Acer boosted shipments by 21% and grew its share by more than two points to 12.7%.

Acer's success was driven by the notebook PC market. In fact, according to the breakdown provided by iSuppli, notebooks accounted for nearly 80% of the Taiwanese's firm shipments last year. But despite its focus on mobile, desktop shipments actually did relatively well, remaining flat in 2009 versus a 15% decline for the market.

Lenovo and Toshiba also increased market share, grabbing 8.2% and 5.1%, respectively. Overall, PC shipments worldwide actually managed to rebound in late 2009 and grew 1% compared to 2008. That's quite impressive considering the year was off to a very bleak start amid a global economic recession.