Last week's column discussed what steps a business should be taking if it already didn't have a plan to deal with the Year 2000 computer bug. "What about my home computer?'' a reader phoned up to ask. "Someone should invent a program to test my computer.'' Well there are such packaged programs.

The major Year 2000 problem exists with the computer system clocks, fundamental to the time keeping functions of the machine. MM&I Technology Group quotes a study which estimates that 93 percent of desktop computers worldwide have Year 2000 defective real time clocks (RTC). The RTCs are chips in the computer's circuitry which store the year with two digits instead of four. The Year 2000 bug describes the inability of the computer to distinguish between years in the 20th century and those in the 21st century.

Here's how the consultancy puts the problem: "The only time the RTC updates its century information is when the computer powers on and the RTC reads information from the BIOS (Basic Input & Output System) clock. So if the computer is turned off before the Year 2000 and powered on afterwards then no problems will arise with the RTC. But if the computer is left on during the transition from 1999 to 2000, then the RTC year fields will be set to "00'' but the century fields will not have been updated, thus the computer will think it is in the year 1900!'' Another problem is some computers will not calculate that Year 2000 is a leap year and will miss the fact that February 29 occurs. Thus days and dates will not match. And certain software and data that use dates to calculate information may also fail if they only use two numbers for the year field.

There are a number of software packages available on the market that will run though your computer and check it to see what needs to be fixed.

"Testing Y2K (the geek terminology for Year 2000) compliance is not as simple as rolling your PC's Windows clock forward and then rebooting the PC,'' MM&I says. "In fact, this should not be done.'' The testing should be performed in the DOS mode and not in the Windows operating systems mode.

"It is far too easy to cause damage to open programs,'' MM&I states in the pitch for its testing software which costs about $100. "It is far too easy to cause damage to open programs. Damage can include corrupting non-year 2000 compatible files. You can also cause installed software licences to expire.

The company instead builds a test disk that runs from a bootable DOS floppy disk. A package program should test whether the computer clocks will produce the correct value when in Year 2000 and beyond, whether the machine is left on or off. A failure in the power off test indicates "a more serious degree'' of hardware non-compliance. The machine then needs to be tested to determine that manually setting the date beyond Year 2000 will be okay.

The software should also test the BIOS clock. MM&I warns: "`Most hardware manufacturers are claiming "Y2K Compliance'' if their machines pass the `powered on' test. Failure in this test indicates that the machine should be left turned off during the roll over period, and if necessary, removed from service and reassigned to another task.'' You're in real trouble if the BIOS clock test fails in the power off test.

Machines failing this test probably will fail the powered off RTC test and often the operating system clock test. The machine will need what's called a "flash BIOS upgrade''.

You'll need software or a technician to tell you the correct BIOS ID update.

Warning: installing an incorrect flash BIOS can cause irreparable damage to a computer, not something for the uninitiated to fool around with.

The software should also test the operating system clock, both in the on and off mode, and what kind of upgrade is needed if necessary. The software will also do a leap year and extended date test.

That's the hardware side. Now for the software tests. A test should look at all executable files, ones that start and run the various applications. The test will then assess the vulnerability of the various software on your computer to the bug.

While nothing seems certain from this description, I'm going to put my computer through the test. And no matter what I'm keeping it off from December 31, 1999 to January 2, 2000. Hope I remember.

Better yet perhaps I'll sell my computer to a sucker on December 31, 1999 and buy a new one on Boxing Day 2000.

Tech Tattle is a column dealing with technology issues. If you have any comments or ideas please contact Ahmed at 295-5881, or 238-3854.

HANDY DEVICE -- A technician holds the $1,999 Sony VAIO 505G Super Slim Notebook computer introduced in New York this month. Weighing less than three pounds and measuring under an inch thick, its features include an Intel 200 MHz Pentium processor.