The accounting review meant Dell would not file its annual report with securities regulators by the April 3 due date, or by an extension date of April 18, the company added.

In its statement, Dell did not give details of the misconduct or of its other findings. A spokesman was not immediately available for comment.

"We still don't know the extent of the misconduct," said Sunil Reddy, senior portfolio manager at Fifth Third Asset Management, which oversees about $21 billion in assets, including Dell shares.

"This news creates uncertainty, but more important are the operational metrics, which need to change in the right direction," Reddy said. "That's going to take some time."

Dell will also review to see whether the control deficiencies "constitute a material weakness" in its internal control over financial reporting. 

Dell announced last August that it had been investigating its accounting for a year. Later in 2006, the company said the U.S. Securities and Exchange Commission and U.S. federal prosecutors were investigating its past accounting.

Founder Michael Dell in January retook the helm of the company from Kevin Rollins, who left after the investigations were disclosed and a series of lower-than-forecast financial results. Also last year, the company lost the No. 1 PC market share ranking to rival Hewlett-Packard Co.

The company in December replaced former Chief Financial Officer James Schneider with former American Airlines chief Donald Carty. Dell, 42, has also made a series of changes to his senior management team, including the appointment of former Motorola Inc. executive Ron Garriques to oversee a new global consumer unit.

The stock fell 6.6 percent to $21.85 in after-hours trading following the announcement, though it recovered slightly and was last down 2.7 percent at $22.75.