As clocks hit midnight on Friday, the widely-feared Y2K computer bug turned into the world's most colossal and costly damp firework. Most computer systems yawned and rolled their dates over to a new millennium without any of the predicted disaster and panic. Now, as analysts put the worldwide cost of fixing the glitch at $600 billion, many are wondering what all the Y2K fuss was about.

Of course, few are complaining that the world seems to have avoided computer system meltdown, except perhaps the technology-hating militiamen holed up in bunkers in Montana.

But sceptics who always believed the 2000 computer glitch was an over-hyped non-event see the lack of global disaster as a vindication of their doubt and resentment. Many suspected the Y2K bug was simply a plot to line the pockets of already prosperous computer programmers, consultancies, and software and hardware companies.

Respected analysts outlined fearful scenarios and governments and businesses had little choice except to heed their warnings. US-based Y2K guru Mr Peter de Jager offered dire Y2K predictions of potential economic collapse and nuclear disaster. Wall Street economist Mr Edward Yardeni envisaged a large-scale recession in 2000 of 1974 proportions as the Y2K bug demolished computer systems.

Analysts Giga Information Group predicted that legal costs resulting from Y2K problems could top $1 trillion.

According to analysts Gartner Group, the world spent between $300 to $600 billion addressing the bug. Analysts IDC offer a more conservative $280 billion, with another $40 billion to be spent in mop-up operations over two years.

The battle to fix non-Y2K compliant systems was led internationally by government agencies, the financial sector and organisations supplying water, electricity, gas, oil, telecommunications and air traffic control. The US placed pressure on other nations to get their houses in order, particularly those in Eastern Europe and Russia.

Many companies, beginning with big corporations such as computer giant IBM, car manufacturers General Motors and major banks, demanded that their business partners prove their systems were Y2K compliant. Government campaigns across the world advised companies to have contingency plans in case of computer failures.

In a relatively low-key campaign, Enterprise Ireland urged Irish companies to update systems and prepare for possible problems.

Fears about air travel kept passengers on the ground and caused cancellations of flights. Many companies told their staff not to fly over the new year for business or pleasure. Wallace Travel Group in Dublin, which has a large corporate clientele, had no bookings at all for January 1st flights and only one tentative reservation for a December 31st flight, according to senior travel adviser Mr Ciaran Wallace.

And in preparation for the actual date rollover on Friday, utilities, governments and companies around the world kept thousands of employees at work or on call. The US government had 800 people on duty in Washington DC. Computer companies were particularly well-staffed: Hewlett-Packard had 20,000 working worldwide, and Microsoft had 6,000, half of which were staffing customer call centres.

In the Republic, Bank of Ireland and AIB both had about 250 employees working, Eircom had 700, and all Government departments had employees monitoring systems and reporting in to a national co-ordination centre set up in the Department of Finance by the National Year 2000 Emergency Co-ordination Committee.

Yet the only problems came when eager parties swamped the phone systems at midnight with happy new year calls.

Mr Joe Macri, head of general sales for Microsoft in Ireland, says Microsoft's European call centre in Britain received less than a dozen calls at the Y2K changeover.

The world's biggest computer network, the Internet, held firm as well, with only minor frustrations for users. Some of the software programs people use to read postings to Usenet, the Internet's jumbo bulletin board, could not read dates correctly and rejected new date-stamped messages.

So has it all been a massive waste of time and money? An IDC chief researcher admitted at the weekend that IDC could not yet show if there would be a "positive return on investment" for the companies which invested millions on Y2K system overhauls. Companies would have lost $21 billion worldwide if system changes were not made, he said.

And most analysts say the night of December 31st, 1999, was only the beginning of a long period in which Y2K-related problems are expected to crop up. Gartner Group has predicted for some time that only 10 per cent of problems would become apparent by January 1st.

Many argue that only minor Y2K-related problems cropped up over the weekend because the systems being monitored across the world were crucial systems which had been carefully overhauled.

In the Republic, some who oversaw system repairs to crucial systems were nonchalant. "We'd done all the remedial work that we thought needed to be done," says one person who led the Y2K project for a large Government department.

Problems which did arise over the weekend point to potential catastrophes which could have come to be. Emergency heart monitoring systems shut down in three Swedish hospitals. Data monitoring systems at several Japanese nuclear power plants went on the blink. France's Syracuse II military satellite system had some glitches, and one US spy satellite shut down for several hours. Minor clock problems surfaced in eight US utility companies and 15 Japanese brokerages had problems processing information. Fortunately all problems had no serious impact.

Yet the story in coming weeks may be different. Most company computer systems have been off or idling over the holiday. Even the major networks which passed the weekend uneventfully have not yet been tested under normal circumstances. Airports have had light traffic and companies have not gone back to a regular workload. No major stock exchange has yet gone through its Y2K paces.

While analysts now say they do not expect a massive hit on systems, they say Y2K problems will keep popping up throughout the year and could be debilitating for unprepared companies. And the February 29th, 2000, date during this leap year is also expected to cause computer problems.

One major computing hurdle may be mostly over but computer angst is clearly going to travel bug-free into the 21st century.