Dell's internal audit has found evidence of misconduct, accounting errors and deficiencies in its financial controls, and it will delay posting its annual results.
The company didn't give details of the findings, saying the investigation wasn't yet complete.
The lastest news comes in the wake of several external investigations into the computer-maker.
Last year, Dell was in the headlines because of an investigation by the US Securities Exchange Commission (SEC), even postponing its third quarter financial report because of the probe.
The SEC and the company's audit committee have been looking into certain accounting and financial reporting matters at Dell.
The commision started an informal investigation into Dell's revenue recognition and accounting practices for previous years in 2005. In August 2005 Dell began an internal financial audit which showed that the company may have misstated prior financial reports, including accruals, reserves and other balance sheet items.
Later, the US attorney for the Southern District of New York also launched an investigation and subpoenaed financial reporting documents going back to 2002.