The new software is the biggest overhaul of Windows in years, and features a new touch-friendly interface dubbed "Metro". It is scheduled to be available for the Christmas shopping season.
The lighter, thinner version of the Surface tablet, built on an Nvidia Corp chip designed by ARM Holdings, will be the first to market at the same time as the general release of Windows 8, and will feature Microsoft's popular Office suite of applications.
It is comparable to Apple's new iPad, heavier but slightly thinner. It has a 10.6 inch screen and comes in 32GB and 64GB memory sizes.
A second, heavier tablet aimed at the new generation of lightweight laptops called "ultrabooks", running on traditional Intel Corp chips, will come in 64GB and 128GB models. That will be available about three months after the ARM version, Microsoft said.
The company gave no details on pricing, except that they would be competitive with comparable ARM tablets and Intel-powered Ultrabooks. They will be on sale online and in Microsoft's new brick-and-mortar stores in the United States.
Microsoft shares rose 0.8 percent in after-hours trading, making up for a 0.6 percent drop to $29.84 in the regular Nasdaq session.
Industry watchers were generally impressed by the devices' specifications, but doubted they were a sure-fire hit.