Research firm Gartner has lowered its forecast for global PC unit sales citing declining mini-notebooks sales and growing popularity of iPads.

Worldwide PC unit shipments are now expected to grow at 9.3% in 2011, reaching 385 million units. Gartner had projected 10.5% growth in March.

Gartner had also said that Global PC shipments in the first quarter of 2011 declined by 1.1% compared to the first quarter of 2010. It said although the first quarter is traditionally a slow one for PC sales, the shipment results indicated potential sluggishness, not just a normal seasonal slowdown.

The research firm now says that throughout much of the last decade, PC unit growth was powered by consumers. However, with consumers from mature markets wary of spending in response to continuing economic uncertainty, and a lack of compelling reasons for consumers to replace their PCs, PC unit growth has slowed. The research company said that PC industry must once again rely on businesses to drive sales.

Gartner research director Ranjit Atwal said consumer mobile PCs are no longer driving growth because of sharply declining consumer interest in mini-notebooks.

"Mini-notebook shipments have noticeably contracted over the last several quarters, and this has substantially reduced overall mobile PC unit growth," Atwal said.

"Media tablets, such as the iPad, have also impacted mobile growth, but more because they have caused consumers to delay new mobile PC purchases rather than directly replacing aging mobile PCs with media tablets, and we believe direct substitution of media tablets for mobile PCs will be minimal."

The research firm said that the in future, PCs will no longer be a market by themselves, but part of a larger device market that ranges from smart televisions to the most-basic-feature phones.

Gartner has also reduced expected 2011 Japanese PC unit growth to 2.4% in response to the March earthquake and tsunami.

Gartner research director George Shiffler said Desk-based PC shipment growth has been significantly affected and business continuity plans are accelerating the shift to mobile PCs and alternate computing models.

"However, the impact of Japan’s twin disasters on worldwide PC shipment growth has been minor, and PC vendors have so far managed the threat of Japanese component disruptions," Shiffler said.