When I travel, I sometimes wonder if the invention of the laptop has contributed to the growth of the chiropractic industry. When you're lugging a 7-pound (or more) machine in one of those 3-pound leather carrying cases through a crowded airport, that portable computer doesn't feel so portable anymore. "Ultralights" or "ultraslims" that tip the scale at a mere 3.5 pounds come closer to providing true portability.

Introduced about a year ago, these machines now boast processors with speeds of at least 300 MHz, internal hard drives of more than 6.0 gigabytes (GB), plenty of memory, adequate video RAM, and a 56 K modem.

It's amazing what a difference a pound or two can make. Ultraslims weighing 3.5 pounds or less, though sleek and attractive, generally lack any internal drives other than a hard drive. So that means no floppy drive or other media drives such as a CD-ROM or DVD-ROM. And though most models have ports that enable you to add an external drive, it is a bit inconvenient if you regularly need to back up data or load software while on the road.

Currently, screens for these models tend to range from a dinky 10.1 inches to an adequate 12.1 inches. There are also keyboard trade-offs-they tend to be more cramped with tiny keys that can be difficult for large hands to peck. As for battery life, you're lucky to squeeze out 2.5 hours. Most models, however, do support a second battery add-on, which can extend the battery life of your laptop as much as 3 additional hours (though some extra batteries can add on as much as 2 pounds to the total weight and cost as much as $450 apiece).

If you desperately require a sturdy but very lightweight laptop for frequent travel, the latest crop of ultralights that weigh between 3.5 and 5 pounds is your best bet. With the extra weight, you can find models that have a hard drive of at least 12 GB, a full-sized keyboard, and a minimum screen size of 12.1 inches. Many also include an internal CD-ROM or CD-RW drive, or even a DVD-ROM drive. Most, however, still won't include an internal floppy drive because the extra weight isn't worth it to most folks.

Prices range dramatically with ultralights. Mainly looking for a secondary PC that will allow you to use your basic office software without any hassle while on the road? For less than $1,500, you can pick up a model that weighs under 3 pounds with a lower end processor like an Intel Celeron, that foregoes any internal media drives, and has a monitor with adequate resolution (around 800 by 600 pixels). Full performance models, particularly ones that include an internal CD or DVD drive, generally start around $2,500.

With prices dropping, finding room in your company budget for an ultraslim may be less back-breaking than actually having to tote your current laptop around.