If your PC is less than 2 years old, it probably contains a newer BIOS that will sail through midnight at century’s end without incident. But if you are using an older machine, and Windows 95 or one of its predecessors, you could see a glitch. The first time you turn your computer on in the new year, you’re likely to see the clock set to 1980.

Even if your PC’s clock enters a time warp, fixing the problem is relatively easy. Just reset the date with normal Windows or DOS commands, and you’ll be fine for the next 100 years (with Windows 95, double-click on the date in the lower-right-hand corner of the screen or go to the Control Panel). It’s like resetting your household clocks for daylight saving time. Microsoft’s current version of Windows NT fixes the BIOS problem automatically. So will the next version of Windows 95, due out next year.

Microsoft advises against performing any tests yourself, such as setting the computer to 11:59 p.m., Dec. 31, 1999, and waiting to see what happens. If your machine contains applications with time limits on them, the software might be fooled into thinking it had expired, or be damaged. If you’re unsure whether your BIOS will trip on the date change, your best bet is to contact the computer manufacturer; 386 and 486 machines may possibly need a BIOS upgrade. Apple Computer assures users that all its Macintosh computers recognize dates up to 2040.

As for your applications, when in doubt, call the software company and ask how year 2000 friendly its products are. Microsoft, for one, points out that all of its products store dates in four-digit form. The makers of Intuit’s popular personal-finance program, Quicken, say it will not go berserk and automatically pay 100 years’ worth of bills for you come 2000. If you’re one of the handful of people using 8-year-old DOS versions (3.0 or below), your program won’t roll over to the year 2000 - but it’s time you upgraded anyway. Microsoft says the same for its Quicken-like Money program (both claims were borne out by informal NEWSWEEK tests).

Whether you should unplug your computer in case your electric power goes haywire is less easy to predict. In general, it pays to take a few low-tech precautionary measures against year 2000 snafus. Keep backup records (both on floppies and on paper) of bank balances, credit-card statements and utility bills. That’s what year 2000 expert Capers Jones is doing. He also plans to enter the next millennium with a full tank of gas in his car (automated gas pumps might spit back his credit card, he worries) and plenty of traveler’s checks in his pocket. Just in case.