Now theyre being targeted by the likes of Sony and startup OQO, who are offering their own diminutive computers for businesses.
But Microsoft and partners—the UMPC has been backed by Intel and VIA Technologies—expect to see more diversity in the UMPC space in the near term.
New manufacturers will bring forth additional usage models and design improvements such as integrated, drop-down keyboards and built-in wireless wide area networking, while also driving down prices.
"Youll see an additional wave of UMPCs available in the holiday timeframe," said Mika Kramer, head of Microsofts new Windows Client Mobility Marketing Team, a group within its Windows Client Product Marketing Group in Redmond, Wash. "We are seeing a lot more Tier 1 players get a lot more interested in releasing the UMPC."
Microsoft has been working with some of those partners to help lower prices and deliver machines in different shapes, styles and colors.
Theres room for designs that target women or teenagers, while others might aim for a business-oriented crowd, according to the software maker.
Meanwhile, Microsofts forthcoming Windows Vista operating system, scheduled for January 2007, will also offer more functionality for UMPCs, and Microsoft will continue updating its Touch Pack or UMPC-specific application bundle, she said.
"Youll definitely see form factors change in the Q4 , Q1  timeframe. Youre going to see integration of different IDs [industrial designs]…and incorporation of keyboards in some machines," Kramer said.
"I think itll be characterized by new entrants in the market. Youll see incremental improvements as time goes by."
Kramer declined to say who might join the UMPC space. Asus, a well-known Taiwanese computer maker, will join this summer, however.
Its 2-pound R2H will offer a 7-inch screen, an Intel Celeron processor and will sell for about $1,000, a company representative told eWEEK recently.
Microsoft will get help from chip makers. Intel, for one, has previewed a low-voltage Core Duo chip that will arrive this summer. VIA Technologies plans to deliver "John," which combines its C7-M processor and VX700M chip set in one package, allowing manufacturers to create very small motherboards for notebooks or UMPCs.
But price, above all, will remain a factor in stimulating demand for UMPCs, analysts said.
"Originally, the concept of the UMPC was to go after consumers, create a new category and attract them with a low price," said Richard Shim, an analyst at IDC in San Mateo, Calif.
But "when we look at the first couple of devices … wheres the low price?"
Indeed, the first brand-name UMPC to ship in the United States, Samsungs Q1, starts at $1,099.
Samsung has positioned the Q1, which is being sold by Best Buy, as a device that can work for both consumers and businesses. Business workers could use the Q1 for keeping track of e-mail and viewing Microsoft Office documents while on the road, Samsung said.
But for about the same amount of money or less, a lightweight laptop could do the same job, analysts say.