Worldwide PC shipments are expected to reach 366.1 million units in 2010, an increase of 19.7% compared to 305.8 million units shipped in 2009, according to a new preliminary forecast by Gartner.

The research firm estimates worldwide PC spending to reach $245bn in 2010, up 12.2% from 2009. In December, Gartner forecast 13.3% growth in PC shipments in 2010 and 1.9% growth in spending.

Gartner anticipates that all regional markets to return to growth and exhibit more normal seasonality in 2010. The firm also expects unit growth to continue to increase strongly over the next few years as home PC demand accelerates and professional replacements rise in the recovery from the global recession.

George Shiffler, research director at Gartner, said: Mini-notebooks are again forecast to boost mobile PC growth in 2010, but their contribution is expected to decline noticeably afterward, as they face growing competition from new ultra-low-voltage (ULV) ultraportables and next-generation tablets. Desk-based PC shipment growth will be minimal and limited to emerging markets.

We expect mobile PCs to drive 90% of PC growth over the next three years. In 2009, mobile PCs accounted for 55% of all PC shipments; by 2012, we expect mobile PCs to account for nearly 70 % of shipments.

The research firm expects that vendors could ship up to 10.5 million traditional tablets and next-generation tablet devices worldwide in 2010.

Ranjit Atwal, principal analyst at Gartner, said: Apple’s iPad is just one of many new devices coming to market that will change the entire PC ecosystem and overlap it with the mobile phone industry. This will create significantly more opportunities for PC vendors as well as significantly more threats.”