Desktops? They're so last year

But price has been the biggest driver in the jump in laptop sales. Desktops have always cost less than laptops, because it's more complicated and more expensive to make compact components for a small machine. In the last four years, though, the price difference has narrowed. Although desktop computer prices have remained relatively flat (buyers today get more bang for their buck), the average price of a laptop has fallen more than 20% as the worldwide market for laptops has opened up and more competitors jump in. Already, some bare-bones laptops can be found for less than $500. The nonprofit One Laptop Per Child initiative is one of several groups trying to bring the price of a portable computer down to $100.

With their newfound popularity, laptops are doing for computing what cellphones did for talking -- bringing the activities into public places. With that, new social norms and rules of etiquette are emerging.

At Ritual Coffee Roasters cafe, a mecca for laptop users in San Francisco, owner Eileen Hassi hired an electrician last spring to disable the electrical outlets. Regulars at the coffeehouse were spending so much time riding the free wireless network -- as many as eight hours at a stretch -- that patrons who wanted simply to sip their lattes couldn't find seats.

You're welcome to work on your laptop here, Hassi explained, "until your battery dies."

Smaller competition

Though laptops have become the growth engine for the computer industry, the line continues to blur between phones and computers. Hand-held devices such as Apple's iPhone are allowing people to do things they could never do before on a phone, such as listen to music, watch videos and easily surf the Web.

The desire to slim down has led computer makers to create a subsection of laptops known as mini-notebooks or sub-notebooks. Sony Corp., for one, makes a $2,499 version for frequent business travelers that weighs 1.2 pounds and features a 4.5-inch screen. (On the flip side, for programmers and video gamers there are laptops known as desktop replacements, or "luggables," that feature huge processors and screens as wide as 20 inches. They weigh as much as 18 pounds.)

And then there's the tablet PC, a hand-held computer with a touch screen that connects wirelessly to a network. Manufacturers have experimented with the tablet PC over the years, but they're making another push to market them to the sales, education and healthcare fields. Last month Dell introduced the Latitude XT, its first tablet PC for less than $2,500, which provides more than nine hours of battery life.