Oppenheimer lowered its profit estimates of Microsoft Corp. (NASDAQ:MSFT) citing a gloomy PC market.

The brokerage reduced its third quarter estimate to earnings of 56 cents a share on revenue of $16.138 billion from earnings of 57 cents a share on revenue of $16.414 billion. Wall Street expects earnings of 56 cents a share on revenue of $16.27 billion, according to analysts polled by Thomson Reuters.

Oppenheimer also trimmed its fiscal 2011 earnings view by a penny to $2.57 a share. The brokerage also cut revenue forecast to $69.925 billion from $70.200 billion. Analysts expect earnings of $2.56 a share on revenue of $69.76 billion.

While calendar 1Q is typically a seasonally weak quarter for PCs, following the release of Gartner's preliminary PC unit data, it is clear 1QCY11 PC sales were even softer than we initially forecasted, analyst Brad Reback wrote in a note to clients.

First-quarter PC sales were flat to down 1 percent year-over-year, below the analyst's initial forecast of about 3 percent growth.

Reback thinks several factors, including headwinds from tablets, the tragic events in Japan, Intel's Sandy Bridge recalls, austerity measures and challenging comps caused PC sales to perform below his expectations.

Although the PC market still struggles, we believe one bright spot remains the professional/enterprise market. We believe the relatively stable macro-economy coupled with pent-up demand is driving solid uptake across large enterprises, Reback wrote.

Additionally, the analyst believes that the small and medium size business refresh-cycle is just getting underway and should aid growth throughout 2011.

While we are disappointed with the weakness in the PC market, we believe much of this is already priced-in and expect multiple expansion as investors gain confidence in MSFT's ability to grow revenue faster than expenses, said Reback, who has an outperform rating on the Microsoft stock.

Microsoft shares closed Wednesday's regular trading session at $25.63 on Nasdaq. Reback has a price target of $36 on Microsoft stock.