New York (MONEY MAGAZINE) - Computer makers -- as well as tech writers -- have long suggested making a laptop your only computer. The appeal is unmistakable: Without a bulky monitor and box, you have more room on your desk; you can use your computer in any room in the house, or even outside; and there's no need to own a second machine for travel.

Unfortunately, the compromises you had to make -- a cramped keyboard and small screen, a slow processor, and minimal memory and hard-drive space -- were steep. Few ports meant you couldn't keep a printer, scanner and another peripheral connected at once. Low-end graphics and sound cards all but ruled out watching movies. In recent years, as components became smaller and prices for liquid crystal display (LCD) screens came down, the promise has inched closer to reality. But the true breakthrough came only this year with Intel's introduction of a Pentium 4 chip for laptops. This fast chip, paired with a new type of RAM that accesses programs twice as quickly as its predecessor did, means that replacing a space-hogging desktop with an equally powerful laptop is more than just wishful thinking. At least eight major computer makers will have P4 laptops on the market by mid-April. And you'll spend only a few hundred dollars more for one than you would have for a similarly equipped PC.

It's more than processor speed that makes the new P4 laptops so appealing. They also hold as much RAM as their desktop counterparts--in most cases, up to 1GB--so you can run a virtually endless array of programs simultaneously. Then there's the screen. You can buy a notebook with an LCD screen that's every bit as good as the flat-panel monitors packaged with new desktops. All the new P4s come with 15-inch LCDs at a minimum -- Sony's goes even further with a 16-inch display. Most of the keyboards are 95% of the size of a typical desktop keyboard, a difference you'll hardly notice.

Say you want to edit your vacation video. P4 portables with DVD/CD-RW drives and high-speed FireWire ports are more than up to the task. If you play sophisticated games with near-realistic images and sounds, like Star Wars Jedi Knight II: Jedi Outcast, you no longer have to default to your desktop. These notebooks come with the best sound and graphics components available.

Of course, these laptops offer one feature your desktop doesn't have: complete portability. Want to do your taxes in the TV room? Feel like working on the deck? No problem. The latest generation of laptops comes with a wireless network technology called 802.11b that lets you go online from anywhere in the house. All you need is a wireless Internet hub, which will cost around $250. A few P4s also have Bluetooth, a wireless technology that's just beginning to catch on. Right now the most common use for it is connecting with Bluetooth-enabled peripherals, like handhelds and printers.

To get all these great features in a small box, you do have to make some trade-offs. The new P4 laptops are bulky and heavy -- most weigh between seven and nine pounds. The big screens and keyboards that make these portables ideal for replacing a desktop also make them less than ideal for a sprint through the airport with one slung over your shoulder. So if you're looking for a laptop mainly for the road, consider one of the sub-three-pound machines hitting the market.

In addition, the P4 processor is battery hungry. Even though Intel says the chip is designed to use less power than the desktop version, a bright 15-inch LCD will suck up juice. As a result, the average battery life for these notebooks is between two and three hours, much less than the four to six hours you can expect from a more portable portable.