Quanta, the world's largest maker of laptop computers, expects healthy demand until the end of the year despite the delayed launch of Microsoft's Windows Vista OS (operating system).

But the Taiwanese company warned that shortages of components, including batteries, microprocessors and memory chips, could affect shipments.

The statement on Vista should assuage some fears of a meltdown in laptop sales ahead of the widespread release of the OS, since Quanta has a broad view of the industry. The company supplies laptops to major PC vendors such as Dell and HP and should have most of its year-end orders already in hand.

The company expects unit shipments to rise by 30 percent in the fourth quarter of this year as a result of healthy demand and the launch of new models. The last three months of the year are typically strong for notebook PCs because of brisk holiday demand.

This year, however, Vista's delayed launch to early next year has put Q4 PC sales in doubt. A number of PC vendors and industry watchers have voiced concerns over a possible downturn late this year as users put off new purchases until after Vista launches.

The new OS places greater demands on PC hardware, and suppliers are already placing Vista-capable stickers on new systems with the configuration to match its requirements, which include 512MB of RAM, an advanced processor and a graphics card.

Vista won't have such a dramatic impact on notebook PC demand, but contract laptop makers in Taiwan say component supply troubles could spoil the Christmas party.

Quanta was the second major laptop computer maker to warn of component supply shortages. Compal, the second-biggest notebook PC maker, blamed a shortage of certain processors and batteries for revising down its unit shipment forecast for Q4. The company predicts it will be able to ship only 4.6 million laptops in the final three months of the year, down from a prior estimate of 4.8 million to 5 million.