Computer maker Dell will reduce more than four years' worth of earnings by up to $US150 million ($A183.52 million) after an internal probe found the company misled its auditors and manipulated results to meet performance goals.

The struggling company said today that its net income for the restatement period will be reduced by between $US50 million and $US150 million ($A61.17 million and $A183.52 million), or two cents to seven cents a share.

The largest reductions in quarterly profits were expected to be in the first quarter of fiscal 2003 and the second quarter of fiscal 2004, each lowered between 10 per cent and 13 per cent.

Dell will restate all of fiscal 2003 through 2006 and the first quarter of fiscal 2007.

The investigation, which began in August 2006 and evaluated more than five million documents, "identified evidence that certain adjustments appear to have been motivated by the objective of attaining financial targets," Dell said.

Round Rock-based Dell added that unspecified terminations, reassignments, reprimands, increased supervision, training and financial penalties either have or will be taken as a result.

"We are committed to achieving and maintaining a strong control environment, high ethical standards and financial reporting integrity," Chairman and Chief Executive Michael Dell said in a statement.

"This commitment will be communicated to every Dell employee and external stakeholder. It is accompanied by renewed management focus on decision-making and processes intended to drive long-term shareholder value."

The Securities and Exchange Commission's investigation into some of Dell's accounting and financial reporting practices is ongoing, the company said.

Dell said the findings would not have a material impact on second-quarter results, which are scheduled for release on Aug. 30.

Dell has issued only preliminary financial results for the four most recent quarters and has not filed its annual report for the fiscal year that ended on February 2 because of the ongoing investigations.

With the internal probe complete, Dell said it expects to file the past-due documents by the first week of November. Its annual shareholders meeting is scheduled for December 4.

Dell still faces shareholder lawsuits, and federal prosecutors in New York subpoenaed documents on the company's financial reporting since 2002.

Dell is the world's second largest PC maker, having recently lost the top ranking to Hewlett-Packard Co.

Dell shares dropped 37 cents, or 1.4 per cent, to close at $US25.93 before the announcement was made.