PALO ALTO -- The most dramatic revamp of Microsoft Windows in almost two decades and the company's first tablet were unleashed to eager customers Friday, a challenge to Apple's (AAPL) much celebrated iPad releases earlier this week.

For months, Microsoft has leaked bits of Windows 8 to the public through demos and online tutorials, pulling back the curtain on what is widely considered a risky and imaginative Windows overhaul. By Friday, Microsoft faithful were eager to take the operating system for a test drive and pick up the company's Surface tablet.

But the day was about more than a system upgrade and a new tablet entering an already saturated market; it also marked a rebirth of the Microsoft brand and the transition into a new way of computing. The new software is designed to be used on touch-screen devices, dramatically changing the user's interaction with a PC and blurring the lines between tablets and laptops.

The excitement was contagious among the 60 or so customers lined up outside the Microsoft store at Stanford Shopping Center in Palo Alto before the doors opened at 10 a.m. Some made reservations to ensure they would have a customized tablet running Windows 8 before the day was over.

Customers said they passed the early morning hours by discussing Halloween costumes

and dancing Gangnam Style -- a dance made popular in a South Korean pop video and looks something like riding a horse.

College student Matthew Deien was first in line, leaving Sacramento at 3 a.m. to arrive at 5:30.

"I thought I was going to be late," he said.

But it was just he and the security guards until another Matt -- Matt Arkin -- arrived about 6 a.m.

Both Matts were there to get Surface, a PC-and-tablet combination with such features as a USB port, SD card slot, click-on keyboard cover and pop-out kickstand. Prices for the 10-inch tablet range from $499 to $699.

Both also said they had already tried out Windows 8.

"It was a little difficult. It was like, where's the desktop? Then you scrolled around a little bit, and it (gets) pretty easy," said Deien, a business student at Sacramento City College.

The new Windows interface is designed around "live tiles," colorful applications arranged on a plain background. Gone are the familiar start button, start menu and -- at least at first glance -- the traditional Windows desktop. Analysts have warned that the system may confuse and frustrate PC users.

Palo Alto store manager Dianna Piccolo said staff are showing customers how to get back to the familiar desktop if they lose their way around the new interface.

"From a PC experience, it's a little unfamiliar," Piccolo said. But most quickly get comfortable after "they just sit back and drive the machine."

Arkin, a developer, had early access to Windows 8 and began using pre-released versions about a year ago. He cautions that the learning curve is about a week and the system may feel clunky on a desktop or laptop.

"You've just got to get used to it," he said.

Microsoft, of Redmond, Wash., recognizes that customers are going to need a bit of help. Stores are offering training and classes throughout the launch, and staff will help customers personalize Windows 8 on their tablets and PCs with everything from their Facebook to their music, said Ted Ladd, who heads store marketing for Microsoft. Customers can bring in their own laptops and get one-on-one training.

"We're focused on making sure it's a white-glove experience," Ladd said.

Microsoft isn't the only place customers can get one-on-one help navigating Windows 8. Best Buy is also hoping to capitalize on the Windows upgrade by offering online tutorials and in-store demonstrations, and taking advance orders of Windows 8 devices.

Windows 8 is also the centerpiece of Microsoft's retail redesign, and stores opened Friday with a new look and new hardware. The Palo Alto store now carries only touch-enabled PCs and window designs that resemble the application tiles. Long tables line the stores and serve as customer workstations -- not unlike the Apple store setup.

The buzz at Microsoft was matched by customers flowing into the Apple store -- just two doors down -- advertising the new iPad Mini announced Tuesday.

But for those already weary with the tablet market, the redesign of Surface and Windows 8 may hit the sweet spot. Marisa Sambuceto said she owns an iPad but bought the Surface because she likes that the tablet allows users to run multiple applications on the screen at once.

"It just seems all around a cooler experience for a tablet," she said. "It seems better than an iPad."

Contact Heather Somerville at 925-977-8418. Follow her at Twitter.com/heathersomervil.