(Reuters) - Hewlett-Packard Co (>> Hewlett-Packard Company) reported flat or lower quarterly revenue in all of its operating units on Tuesday, and forecast full-year earnings well below analysts' expectations due to a strong U.S. dollar.

Its shares tumbled 6.7 percent in after-hours trading.

The world's No. 2 PC maker, which has struggled to adapt to the new era of mobile and online computing, is preparing to split into two listed companies later this year, separating its computer and printer businesses from its faster-growing corporate hardware and services operations.

"Revenue was a little short on the top end, the guidance for the second quarter was a little below where the consensus was," said Daniel Morgan, a portfolio manager at Synovus Trust Co.

"Let's wait till October, see if this split is really going to create the shareholder value that (CEO) Meg Whitman is hoping for."

HP has not projected the total cost of its separation plan but it said on Tuesday it will take charges of $1.3 billion this fiscal year and $500 million next year to pay for the move.

On top of that, it forecast an extra $300 million this year in capital spending related to the plan, plus $950 million in foreign tax expenses, although it said more than half of the tax cost could be recuperated.

The combined effect of those separation costs and the hit from the strong dollar will almost halve HP's free cash flow this fiscal year to about $3.5 billion to $4 billion, down from a forecast three months ago of $6.5 billion to $7 billion.

Palo Alto-based HP follows Microsoft Corp (>> Microsoft Corporation) and International Business Machines Corp (>> International Business Machines Corp.) in seeing a significant negative impact from the strong dollar. HP took about two-thirds of its revenue from outside the United States in the year ended October 2014. The dollar <.DXY> had risen 14.7 percent in the last six months through Tuesday.

HP said it expected adjusted profit of $3.53 to $3.73 per share for the full year ending October, due to a 30 cents per share hit from currency factors, well below analysts' average estimate of $3.95.

Overall revenue dropped 4.7 percent to $26.84 billion in the first quarter ended Jan. 31.

The computer and printer units, which will make up HP Inc under the separation plan, saw combined revenue fall 1.8 percent from the year-ago quarter to $14 billion, while the rest of the company, to be known as Hewlett-Packard Enterprise, saw revenue fall 4.9 percent to about $13.6 billion.

But pre-tax profit from what will become HP Inc grew more slowly, up 10 percent to almost $1.4 billion, compared with the Hewlett-Packard Enterprise units that posted a 13 percent increase to about $1.5 billion.

The company's overall after-tax net income fell to $1.37 billion, or 73 cents per share, from $1.43 billion, or 74 cents per share, a year earlier. Excluding items, the company earned 92 cents per share.

Analysts on average had expected a profit of 91 cents per share and revenue of $27.34 billion, according to Thomson Reuters I/B/E/S.

HP shares fell 6.7 percent to $35.90 in after-hours trading. Up to Tuesday's close of $38.49, the stock had risen 9.3 percent since the company announced the split in October.

(Reporting by Abhirup Roy in Bengaluru and Bill Rigby in Seattle; Editing by Sriraj Kalluvila, Gunna Dickson and Ken Wills)