In the world of notebook computers, "low-cost" used to mean "virtually useless." But today's laptops offer dramatically more for the money. A good example: the Versa 2000 series from NEC Technologies (800 632-8377). For a street price of just under $2,000, you can now get a laptop with a 10.4-inch passive-matrix color display, a 75 megahertz 486 processor, a removable 350 megabyte hard drive, and a built-in fax modem. Most users will want to spend about $200 more to double the standard RAM to 8 megabytes. Other options include an active-matrix display and hard drives to 720 megabytes.