The restatement period includes the financial year 2003 to 2006, and the first quarter of fiscal 2007.
The company said the internal probe, which began in August last year, identified "evidence that certain adjustments appear to have been motivated by the objective of attaining financial targets".
Following the findings, Dell said unspecified terminations, reassignments, reprimands, increased supervision, training and financial penalties either have or would be taken.
"Let me assure you that both the leadership team of the company and the board feels that we have absolutely taken the necessary action"
The Securities and Exchange Commission (SEC) is separately investigating some of its accounting and financial reporting practices, the company added.
Dell said the findings would not have a material impact on second-quarter results, which are scheduled for release on August 30.
The company still faces shareholder lawsuits, and federal prosecutors in New York subpoenaed documents on the company's financial reporting since 2002.
Since August, Dell has seen some significant changes in its executive line-up including the departure of James Schneider, its former chief financial officer, and the return of Michael Dell as its chief executive officer.
Don Carty, who replaced Schneider in December, said the ones who were privy to the accounting woes "are the ones that are gone".
"Let me assure you that both the leadership team of the company and the board feels that we have absolutely taken the necessary action," he said.
Since losing the top place in the PC market last fall, Dell has retooled its products with a new focus on design, some with flashier colours.
One analyst said the financial impact of the probes appeared minimal given Dell's multibillion-dollar size.
Dell shares dropped 37 cents, or 1.4 per cent, to close at $25.93 before the announcement was made. The stock rebounded 42 cents in after-hours trading.