Sure, making backups is no fun.

But it's a lot less fun spending grueling days or weeks manually rebuilding all your computerized form letters, ledgers and scintillation counts lost to a thief, disaster or carelessness.Data-destroying disaster strikes virtually every computer user at least once. If you're running a computer for business, education or research, there's only one way to avoid torture and expense: regular backups.

Backups you make with the DOS program called "backup" are different from programs and files duplicated using "copy." One difference is that the backup program can tell which files you didn't change since the last backup. If you like, it will back up only changed files, saving time and space on your backup disks, tapes or CDs.

A more important difference is this: You can only recopy these files back onto your primary storage disks using the DOS command "restore." Many clients we've computerized, such as medical offices and pharmacies, depend on historic computer data for a livelihood.

To keep that data safe, we devised the 1-1-1-1-1 system: one a day, one a week, one a month, one a year, and one before installing every new piece of computer hardware or software.

Stick to our system until you find a better rhythm. The important thing is to stay with it day in and day out.

Make daily backups the core of your routines. Back up any computer each day it's used more than three hours. We use tape backups, but the advice is the same if you use floppies or CDWORM.

For our dailies, we rotate a set of tapes labeled MON, TUES, WED and THURS. On Friday, we dig into our weekly tapes. They're labeled WK-1, WK-2, WK-3 and WK-4. For WK-5, we use our monthly rotating stock. We close our financial books after the end of each month. More than once, we've used WK-5 to restore the way our journals looked before closing the books. For you, WK-1 or WK-2 may make a better monthly backup.

We label monthly tapes for each month, using 15 in all. We keep a fiscal year's tapes for three months after closing a year's books. If a horrible mistake shows up, we'll be amply rewarded. If you don't need that much of a safety chain, do keep at least one month's overlap.

Our total tape count is 23. Sure, the $500 was a big initial investment. But we can amortize it over at least the next ten years.

What do you use to make your backups, floppy disks, tapes or what? Did you choose the medium or did it choose you? We moved from floppies to tape backup years ago, soon after trading our NEC CP/M computers for MS DOS. We like it because it's much faster and more reliable. If you're doing a lot of disk-changing during weekly backups, think about switching, too.

If you own a Macintosh or IBM-compatible, you can buy an add-on backup tape system for anywhere from a few hundred dollars to several thousand. We're partial to Irwin's add-on tape drives. We especially like the software they come with.

If Irwin's too rich for your taste, look at other brands.

The switch from floppies to tapes is much more significant, in our opinion, than the difference between the various brands.

The software that comes with each tape drive nicely automates backup procedures. All the software we've seen is very good, but for more money you get more features. We can set our Irwin software to back up a predetermined set of files each day - and to actually start itself automatically at the time of day we've set it for. That feature takes a lot of the drudgery out of backing up.

Besides buying tape backup hardware, you'll need to spend $20 to $40 per tape. Each tiny cartridge backs up from 20 to 2,000 megabytes (2 gigabytes), so most buyers can easily get an entire disk backup onto one tape.

If two gigabytes of storage space seems like peanuts to you, look at the new CD-WORM and CD-Erasable backup systems. We described their cost and benefits in a recent column. (We'll be happy to send a reprint of the column if you request it enclosing a stamped, self-addressed envelope.) If you can't yet afford a tape system, or use the computer less than eight or 10 hours a week, floppy disks are fine for backups. It takes more time but your outlay is just the cost of the disks.

But if you use a 5.25-inch disk drive for making backups, avoid the 1.4M IBM-compatible format. It crams a lot of data in a little space, but as your disk drive gets older, its data read-write head slowly changes in alignment. It's not enough to mess up the head's ability to read low-density disks. But high-density disks become unreliable faster than any other floppy format.

Plan for one yearly expense even if you don't use high-density disks: You must have your floppy disk drives cleaned and adjusted annually. It's a good idea to do the same with tape drives, but with them less rigorous maintenance isn't as dangerous.

Lots of software is sold on the promise that it makes backing up to floppy disks easier. We're wary of the lot. These utilities rarely get a real test until disaster requires you to restore backed-up files. That's absolutely the wrong time to find out if what you have works with your hardware and your software.

The backup utilities that come with Macintosh and IBM-compatible operating systems are easy to use for making backups to floppy disks. If you must buy another helper, test it vigorously before you begin counting on it.