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The weekend can't start soon enough for Microsoft CEO Steve Ballmer, who watched as investors drove down the company's stock by more than 11 percent Friday after a disappointing earnings report raised questions about demand for the latest Windows operating system as well as the Surface tablet.

The stock finished at $31.40, off $4.04 for the day. The percentage decline -- which wiped out more than $32 billion in stockholder value -- was the biggest slide in Microsoft's stock since the year 2000. More than 245 million shares traded hands compared with the 90-day average trading volume of 50 million.

On Thursday afternoon, Microsoft announced its fiscal fourth-quarter earnings and the report again raised questions about the CEO's bigger strategy. On the surface -- no pun intended -- the company posted decent numbers. Microsoft's net income was $4.96 billion, compared with a $492 million loss during the year-ago quarter. Revenue rose 10 percent to $19.9 billion. Unfortunately for Microsoft, the earnings were about 9 cents shy of Wall Street expectations.

The report also triggered new worries as sales by the Windows division fell almost 6 percent from the year-earlier period. Microsoft also took a $900 million write-down related to unsold inventory of its Surface tablet. It also fed the flames about the CEO's ability to navigate the company successfully into the post-PC era.

Earlier in the day, Nomura Securities' Rick Sherlund, an analyst who has followed Microsoft since the 1980s, put out a note to clients that bluntly questions the chances for success of a recent corporate reorganization that Ballmer announced last week. That move calls for the elimination of the current five Microsoft business units along with merging all three Microsoft operating systems into a single division. Also, marketing and business strategy decisions will get centralized in cross-company groups. The hoped-for upshot will be a more agile and responsive tech company. But Sherlund took a dim view of the reshuffle after going through the latest numbers.

"The recent reorganization does not fix the tablet or smartphone problem," he said. "The devices opportunity just received a $900 million hardware write-off for Surface RT and investors may not even like the idea of wading deeper into this territory."