Although worldwide PC shipments increased 2.6 percent from Q2 2010, that number is short of IDC's projections for 2.9 percent growth, with the main culprits being competition from smartphones and tablet PCs, a dwindling netbook market in the U.S. and "pressure from lackluster economic conditions."

Within enterprises, a shift in spending to cloud and virtualization technologies has also softened PC demand, according to the .

The United States was one of the weaker regions in IDC's report. Second-quarter PC sales in the U.S. were down 4.2 percent over the same period last year, according to IDC.

Another factor at play for the lackluster PC sales: The drunken-sailor-type spending on PCs in the second quarter of 2010, which raised the bar for this year, says IDC research analyst Rajani Singh, in a news release.

"The impact of 2Q10's difficult-to-sustain 12 percent growth" has led to continued contraction this quarter, Singh said.