The computer empire of Michael S. Dell spreads across a campus of low-slung buildings in Round Rock, Tex.

But his financial empire — estimated at $16 billion — occupies the 21st floor of a dark glass skyscraper on Fifth Avenue in Manhattan.

It is there that MSD Capital, started by Mr. Dell 15 years ago to manage his fortune, has quietly built a reputation as one of the smartest investors on Wall Street. By amassing a prodigious portfolio of stocks, companies, real estate and timberland, Mr. Dell has reduced his exposure to the volatile technology sector and branched out into businesses as diverse as dentistry and landscaping.

Now, Mr. Dell is on the verge of making one of the biggest investments of his life. The 47-year-old billionaire and his private equity backers are locked in talks to acquire Dell, the company he started with $1,000 as a teenager three decades ago, in a leveraged buyout worth more than $20 billion. MSD could play a role in the Dell takeover, according to people briefed on the deal.

The private equity firm Silver Lake has been in negotiations to join with Mr. Dell on a transaction, along with other potential partners like wealthy Asian investors or foreign funds. Mr. Dell would be expected to roll his nearly 16 percent ownership of the company into the buyout, a stake valued at about $3.5 billion. He could also contribute additional personal money as part of the buyout.

That money is managed by MSD, among the more prominent so-called family offices that are set up to handle the personal investments of the wealthy. Others with large family offices include Bill Gates, whose Microsoft wealth financed the firm Cascade Investment, and New York’s mayor, Michael R. Bloomberg, who set up his firm, Willett Advisors, in 2010 to manage his personal and philanthropic assets.

“Some of these family offices are among the world’s most sophisticated investors and have the capital and talent to compete with the largest private equity firms and hedge funds,” said John P. Rompon, managing partner of McNally Capital, which helps structure private equity deals for family offices.

A spokesman for MSD declined to comment for this article. The buyout talks could still fall apart.

In 1998, Mr. Dell, then just 33 years old — and his company’s stock worth three times what it is today — decided to diversify his wealth and set up MSD. He staked the firm with $400 million of his own money, effectively starting his own personal money-management business.

To head the operation, Mr. Dell hired Glenn R. Fuhrman, a managing director atGoldman Sachs, and John C. Phelan, a principal at ESL Investments, the hedge fund run by Edward S. Lampert. He knew both men from his previous dealings with Wall Street. Mr. Fuhrman led a group at Goldman that marketed specialized investments like private equity and real estate to wealthy families like the Dells. And Mr. Dell was an early investor in Mr. Lampert’s fund.

Mr. Fuhrman and Mr. Phelan still run MSD and preside over a staff of more than 100 overseeing Mr. Dell’s billions and the assets in his family foundation. MSD investments include a stock portfolio, with positions in the apparel company PVH, owner of the Calvin Klein and Tommy Hilfiger brands, and DineEquity, the parent of IHOP and Applebee’s.

Among its real estate holdings are the Four Seasons Resort Maui in Hawaii and a stake in the New York-based

developer Related Companies.

MSD also has investments in several private businesses, including ValleyCrest, which bills itself as the country’s largest landscape design company, and DentalOne Partners, a collection of dental practices.

Perhaps MSD’s most prominent deal came in 2008, in the middle of the financial crisis, when it joined a consortium that acquired the assets of the collapsed mortgage lender IndyMac Bank from the federal government for about $13.9 billion and renamed it OneWest Bank.

The OneWest purchase has been wildly successful. Steven Mnuchin, a former Goldman executive who led the OneWest deal, has said that the bank is expected to consider an initial public offering this year. An I.P.O. would generate big profits for Mr. Dell and his co-investors, according to people briefed on the deal.

Another arm of MSD makes select investments in outside hedge funds. Mr. Dell invested in the first fund raised by Silver Lake, the technology-focused private equity firm that might now become his partner in taking Dell private.

MSD’s principals have already made tidy fortunes. In 2009, Mr. Fuhrman, 47, paid $26 million for the Park Avenue apartment of the former Lehman Brothers chief executive Richard S. Fuld. Mr. Phelan, 48, and his wife, Amy, a former Dallas Cowboys cheerleader, also live in a Park Avenue co-op and built a home in Aspen, Colo.

Both are influential players on the contemporary art scene, with ARTNews magazine last year naming each of them among the world’s top 200 collectors. MSD, too, has dabbled in the visual arts. In 2010, MSD bought an archive of vintage photos from Magnum, including portraits of Marilyn Monroe and Mahatma Gandhi, and has put the collection on display at the University of Texas, Mr. Dell’s alma mater.

Just as the investment firms Rockefeller & Company (the Rockefellers, diversifying their oil fortune) and Bessemer Trust (the Phippses, using the name of the steelmaking process that formed the basis of their wealth) started out as investment vehicles for a single family, MSD has recently shown signs of morphing into a traditional money management business with clients beside Mr. Dell.

Last year, for the fourth time, an MSD affiliate raised money from outside investors when it collected about $1 billion for a stock-focused hedge fund, MSD Torchlight Partners. A 2010 fund investing in distressed European assets also manages about $1 billion. The Dell family is the anchor investor in each of the funds, according to people briefed on the investments.

MSD has largely remained below the radar, though its name emerged a decade ago in the criminal trial of the technology banker Frank Quattrone on obstruction of justice charges. Prosecutors introduced an e-mail that Mr. Fuhrman sent to Mr. Quattrone during the peak of the dot-com boom in which he pleaded for a large allotment of a popular Internet initial public offering.

“We know this is a tough one, but we wanted to ask for a little help with our Corvis allocation,” Mr. Fuhrman wrote. “We are looking forward to making you our ‘go to’ banker.”

The e-mail, which was not illegal, was meant to show the quid pro quo deals that were believed to have been struck between Mr. Quattrone and corporate chieftains like Mr. Dell — the bankers would give executives hot I.P.O.’s and the executives, in exchange, would hold out the possibility of giving business to the bankers. (Mr. Quattrone’s conviction was reversed on appeal.)

The MSD team has also shown itself to be loyal to its patron in other ways.

On the MSD Web site, in the frequently asked questions section, the firm asks and answers queries like “how many employees do you have” and “what kind of investments do you make.”

In the last question on the list, MSD asks itself, “Do you use Dell computer equipment?” The answer: “Exclusively!”

This post has been revised to reflect the following correction:

Correction: January 18, 2013

An earlier version of this article misstated when an MSD affiliate raised money from outside investors for a hedge fund. It was last year, not earlier this year. The article also misstated which hedge fund and its focus. It was MSD Torchlight Partners, a stock-focused hedge fund, not MSD Energy Partners, an energy-focused hedge fund.

A version of this article appeared in print on 01/18/2013, on page B1 of the NewYork edition with the headline: Michael Dell’s Empire In a Buyout Spotlight.

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