You've got precisely 24 hours to get the quarterly sales report to the chairman -- and all of a sudden your computer won't even turn on. The home office is sending out a hotshot from accounting to audit your operation -- but she uses DOS software, and you're a pure Macintosh shop. You've just hired an office temporary for a crash three-week project -- but there's no computer available for him to use.

For each of those dilemmas, one solution would be to rush out and buy a new computer to deal with the short-term need. But there is a better way.

Because people keep running into problems like these, the personal computer rental business is on a tear. Analysts say the rent-a-PC industry is growing at a rate of 35 percent a year. The Wall Street Journal estimates that renting small computers has become, all of a sudden, a $500-million-per-year business.

Perhaps the surest sign that PC rental has come of age is the interest shown by some of the biggest names in the computer trade. Businessland, probably the number one computer retail chain, is setting up a new chain of rental stores, "Businessland Rents," with outlets on the coasts and in Chicago. IBM is now letting authorized dealers rent its PCs with an official imprimatur.

To find a computer rental firm, just open the Yellow Pages and peruse the local listings. The local rental trade is particularly lively in places like Las Vegas and Chicago, where the regular presence of big trade shows means there's always somebody looking to rent one or more PCs.

Recently, though, there have been efforts to create national rental operations.

GE Rents (1-800-437-3687), a General Electric division based in Atlanta, offers rentals by the day, week, month or year and promises quick delivery nationwide.Personal Computer Rentals (1-800-922-8646) is a franchise operation with 60 locations nationwide. It, too, will ship computers to your site, but the chain of local outlets can make things more flexible if there's a rental location near you.

We should make it clear here that we are using the term "rental" to mean a short-term arrangement -- borrowing a computer for a couple of days or weeks.

It has been possible to lease PCs for a year or more, but that's really a different question. While leasing would seem to make sense for an innovation-sensitive product like the computer, rates run so high that it's often cheaper to buy a machine though it may be obsolete in two or three years.

The rental trade, in contrast, is designed to get you over those short-term humps. Renting can be a dollar-wise alternative to buying a new computer, even though daily rental rates are pretty steep.

A recent edition of Personal Computer Rentals's standard price list, for example, showed that it cost $277 to rent a Macintosh II with a 40 megabyte hard drive for one day; one week cost $443. Adding a Laserwriter printer raised the bill by $233 for a day or $373 for a week. An IBM PS/2 Model 70 cost $287 for a day and $459 per week; adding a Laserjet raised that bill by $175 per day or $233 per week.

Of course, every peripheral you need adds to the tab. Personal Computer Rentals charged $35 for a day and $59 for a week to rent a 2400-baud Hayes modem. A high-resolution IBM 8514 color monitor -- the kind you'd want to use for a presentation or trade show -- rented for $70 for one day or $111 for a week.

A month or so at those prices, and you could have purchased a clone system instead of renting. But for a couple of days or weeks, renting can be less expensive than buying a system you don't really need. And if you need a machine just for a three-day convention in Boca Raton, it's probably cheaper and safer to rent than to ship the office computer and printer to Florida.

Those national rental operations, by the way, tend to have the highest prices. You might save something by trying a local store. Not long ago, I needed an Apple Laserwriter for a specific job. A mom-and-pop rental outlet found in the Yellow Pages provided one for three days for $100, plus a delivery charge.

If you rent a PC, the renter will generally assume that you know how to run the thing: You're paying for equipment, not training. Most rental operations put DOS and perhaps a few utility programs on the hard disk, but for the most part it's up to you to provide the software. Software rental might make sense as a business proposition, but the software houses seriously discourage this trade because of a fear -- probably warranted -- that unscrupulous renters would just copy the program and save the purchase price.

Renting a PC doesn't meet every need. But when you have to have it, the good news is that a short-term computer is available just about everywhere these days.