A friend I'll call Janet needed to buy a new MS-DOS computer. That's simple enough -- you can find them in every size and style in any American city. But Janet had a few conditions that made things slightly difficult. The solution she finally hit on is instructive for anybody who is in the market for low-priced computing power.

For one thing, Janet wanted to run Microsoft Windows and some other memory-hungry software, so she needed at least 2 megabytes (2 million bytes) of random-access memory (RAM). And if you're buying that much memory, it makes sense to buy a computer equipped with an 80386 or 80486 microprocessor because earlier microprocessor chips, such as the 8086 and 80286, can't make much use of memory beyond 640,000 bytes.

Since Janet already was using a sharp VGA color monitor on her old PC, she wasn't about to go back to a less attractive display. Like many users, she needed a PC with both 3 1/2-inch and 5 1/4-inch floppy disk drives in addition to a 40-megabyte hard disk.

Finally, Janet wanted to buy her new PC for no more than $1,500, including all taxes, delivery and set-up charges. Could this be done?

At first blush, it looked like the answer was no.

Yes, prices for high-powered PCs have been dropping, particularly for machines built around the 80386SX microprocessor, a bargain-priced cousin of the standard 80386 chip. It is possible, through discount retail chains like Compu-Add or big mail-order houses like Gateway or Zeos, to buy a 386SX PC with VGA color display and a 40-megabyte hard disk for about $2,200, plus shipping. But while that's a terrific price, it was still too high for Janet's budget.

So Janet did some thinking. Since she already had a VGA display board and monitor on her old PC, she didn't need to buy those parts again. In the MS-DOS world, peripherals like display boards and monitors are standardized. They'll run on any machine.

Then Janet started prowling around for a bargain-basement 80386SX computer. While many retail stores do offer no-name MS-DOS clone machines for low prices, Janet couldn't find a store that would supply a computer within her tight budget.

That meant Janet would be forced to buy via mail-order. Mail-order computer dealers generally offer lower prices than retail stores. But the mail-order buyer has none of the advantages that go with buying from a local retailer: the friendly advice, the set-up and delivery help, and the easily accessible service facilities..

Many mail-order computer ads feature big headlines promising an 80386SX computer for $999, or some such. When you read the small print, it turns out that this is just a base price -- little things like memory, display, keyboard and delivery add to the price.

Still, Janet found not just one, but half a dozen mail-order houses offering 80386SX PCs with 40-megabyte hard drive for less than $1,500. Generally, these came with 1 megabyte of RAM memory -- not enough to run Windows at a reasonable rate of speed. But most firms were willing to throw in a second megabyte of RAM for about $100 more.

Janet finally decided to buy from a Phoenix outfit called FastMicro (800-441-3278). This company included a full 2 megabytes of RAM in its base price of $1,300 for a 386SX PC.

That model came with a single floppy-disk drive. Adding a second drive cost $79. To save desk space, Janet decided to buy the "small footprint" version of the computer, which added another $50. A copy of the MS-DOS operating system was also priced separately, adding $69. FastMicro's basic model includes a monochrome display board and monitor. Janet was going to use her own VGA display, so the firm was willing to drop the display equipment and cut $100 from its price.

The standard freight charge for shipping this computer was $39.84. Like most mail-order stores, FastMicro charged no sales tax for deliveries outside its home state. When everything was totaled, the price for Janet's new computer made it within the $1,500 budget with room to spare: $1,436.84.

Janet didn't know whether to be thrilled or terrified when the huge boxes showed up at her house. But when she installed her old VGA board in the FastMicro machine, hooked up her old monitor, and flipped the switch, the machine came to life. It's been working perfectly ever since.

Not everything was perfect. The mail-order house sent a monitor that Janet hadn't ordered, so she had to call to have it picked up. When she needed help installing the new version of DOS, it took a half dozen tries to get through to FastMicro's overworked technical staff.

On the whole, though, the experience was positive. Janet learned a key fact: If you're willing to look around, do some work and take a chance on mail-order, you can get a high-powered, full-featured PC for peanuts.