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Bill Gates is planning to show off his new home in style. The co-founder of Microsoft (and one of the world’s richest people) is inviting 200 of the nation’s top CEOs to his $50 million waterfront estate in May to celebrate completion of the highly publicized structure.

The bash is being coordinated by Forbes magazine, which has a history of high-profile partying.

Microsoft sources have kept the event quiet because of security issues. But Gates spokeswoman Shelby Barnes now says the completion of the roughly 45,000-square-foot complex in Medina, Wash., the opulent suburb on Lake Washington’s east shore just east of Seattle, is now officially set, or re-set, for spring.

In seven years of planning, construction and delays, the concept has strayed little from the “adventurous house” Gates described a decade ago. It’s still a billionaire’s estate featuring futuristic computer technology to change wall art, room temperature, music and lights as visitors or residents go room to room.

Only the telephone closest to the person called will ring. Guests will be dazzled by a wall of 24 video monitors featuring art, film, or as-yet-unthought-of possibilities.

The complex still has a 20-seat theater, a 60-foot-long pool with underwater music, a 100-foot pier, a 20-car underground garage, an indoor-outdoor spa, a $1.4 million caretaker’s residence, a 1,700-square-foot guest “cottage,” a 100-visitor reception hall, arcade, lakeside pavilion, racquetball-volleyball court and indoor trampoline pit with a 20-foot ceiling.

Built into the contour of the hillside, the complex has a woody, windowy Northwest architectural style: lots of exposed wood, rock, concrete, flowing wooden stairways and open space.

There have been changes. The 5-acre, 45,000-square-foot complex began as a bachelor pad, albeit with bedrooms for three children and a nanny .

Those possibilities started coming true in 1994 when Gates married Microsoft executive Melinda French. Their daughter was born last spring. Melinda Gates added a study for herself, redesigned the kitchen and hired an interior-designer to make the house less a convention center and more a home.

About seven drawers of building plans on file at Medina City Hall show the house uses lots of nickel plating: nickel-plated bathtubs, light switches, fixtures and more.

The biggest change: the ever-ballooning price tag, which began at around $10 million.

Barnes said the tab now roams around “$40 million to $50 million,” but property records suggest it leans toward $50 million.

Then there’s $559,253 for retaining walls and at least $2 million more for the first 350 feet of Gates’ 500-foot shoreline. Never mind the cost of furnishings.

The price tag has helped to improve Medina’s bottom line. To refile for the main residence’s building permit in June 1995, Gates paid the city an $84,653 permit fee and a $55,027 plan-check fee.

He may have to pony up another $139,680 to get an extension on the permit until next spring.