Dell Inc. (DELL) agreed Monday to buy information-technology service provider Perot Systems Corp. (PER), long seen as a potential Dell target, for $3.9 billion as the world's No. 2 computer seller looks to expand on its core personal-computer business.

The acquisition creates a company with $8 billion in services revenue as Dell seeks to better position itself among more diversified rivals such as Hewlett-Packard Co. (HPQ) and International Business Machines Corp. (IBM) that already have substantial services units.

Dell was widely expected to acquire an IT services company following H-P's purchase of Electronic Data Systems in 2008. In recent years, companies that supply computers and other hardware have been combining those products with services - such as providing customer support or managing data centers and computer networks - which offer new growth areas and recurring revenue streams.

Perot Systems was founded in 1988 by H. Ross Perot, who earlier created Electronic Data Systems and subsequently ran unsuccessfully for president of the U.S. in 1992 and 1996. The company specializes in IT services and consulting, with nearly half of its revenue coming from the health-care industry and a quarter from the government sector.

Dell will begin a tender offer to buy all the class A shares of Perot for $30 a share, a hefty 68% premium to Perot's closing price Friday of $17.91. Perot's class A shares haven't been above $30 for more than a decade.

The deal is expected to close by the end of January but isn't seen adding to Dell's earnings until fiscal 2012. In the first year, the deal is expected to be "modestly dilutive," company officials said in a conference call to discuss the acquisition. In two years, Dell expects it will be able to cut roughly 6% to 8% of $4 billion in combined costs between the two companies. Dell reported the second quarter of its fiscal 2010 last month.

Dell shares fell 3.2% to $16.15, and Perot Systems added 65% to $29.63. Given the deal's high premium and Dell's cash position, it's unlikely another bidder might approach Perot.

Dell already provides some IT services, but the vast majority of its revenue, around 80%, comes from corporate computer purchases. Perot will allow Dell to expand into more sophisticated services, such as building and managing large, complex computer networks.

H-P, the world's largest computer maker, purchased EDS last year for $13.9 billion at a comparatively lower premium of 33% to Dell's purchase of Perot.

Dell's buy of Perot "was a relatively expensive acquisition," Shannon Cross of Cross Research said, adding that Perot is a much smaller acquisition than that of EDS by H-P and more of a "bolt-on" for Dell. The higher price, she said, could also reflect that there were few other services companies for Dell to purchase.

"There aren't that many candidates out there," she said.

The move follows months of speculation as to whom Dell, which had $11.7 billion in cash as of July 31, would buy in order to fill gaps or strengthen weak spots in its business products portfolio.

The talk increased this summer after Dell hired David Johnson, the former chief of mergers-and-acquisitions strategy at IBM, which tried unsuccessfully to block the hiring in courts. Dell added more financial firepower by selling $1 billion in bonds.

Dell is expected to expand Perot's reach farther across the globe. Perot had been seeking to expand internationally to reduce its exposure to the U.S., and the two companies already partner on some projects. As the integration of Perot progresses, Dell expects to add smaller services acquisitions to bolster Perot's geographic reach.

Perot will become Dell's services unit and will be led by its current chief executive, Peter Altabef. Also, Dell's board will consider Perot Chairman Ross Perot Jr. for a seat.

Dell said retaining Perot Systems employees is critical to the acquisition's success, adding that it has already signed long-term retention agreements with several senior executives.

Last month, Perot said its second-quarter profit rose slightly thanks to improved margins despite a drop in sales, but it gave a third-quarter revenue forecast below analysts' expectations. For 2009, analysts on average project Perot's earnings to rise 2% to $117.3 million and revenue to fall 9% to $2.53 billion, according to Thomson Reuters.

Meanwhile, Dell posted a 23% profit drop last quarter as it continues to suffer from weak spending in technology, particularly by corporation. For Dell's fiscal 2010, which ends in January, analysts see earnings falling 22% to $2.08 billion and revenue dropping 15% to $51.63 billion.

-By Jerry A DiColo, Dow Jones Newswires; 212-416-2155; Jerry.Dicolo@dowjones.com

(George Stahl and Joan E. Solsman contributed to this article.)