Microsoft has pushed back the consumer release of Windows Vista to January 2007, because it isn't good enough to meet its Q4 2006 target.Instead, Microsoft has staggered the launch into two parts - subscribers to Microsoft's Volume Licensing Program will be able to get the code in November 2006, while OEMs can begin shipping it in January next year.

"We needed a few more weeks," said Windows boss Jim Allchin. "We decided to optimize it for the entire industry."

That's nice. But did Microsoft only just realize it needed to do this?

Allchin said the next beta (that's "CTP", or Community Technology Preview in Redmondspeak) was on track to go to 2 million testers. He was vague on the reasoning, but mentioned quality foremost.

It's a delay that hurts PC builders far more than it hurts Microsoft - because Microsoft gets to collect a license fee for every PC sold, so long as it ships with some copy of Windows. OEMs had been hoping a Fall launch, with its accompanying marketing blitz, would boost retail sales of consumer PCs. Now they must subsidize the January upgrade, or hope consumers don't get wise, and hold off until the New Year.

Bill Gates liked to compare Longhorn to the Apollo space program, but it's become less of a Moonshot and more of a Moonwalk as successive targets have tip-toed backwards.

Harking back to the days of the XP beta "Whistler", which was regarded as a code cleanup and facelift for Windows 2000, Microsoft planned the all-singing, all-dancing upgrade "Blackcomb" to be released in 2003 or 2004, with what we called a coffer-filling release to emerge in late 2002 or early 2003.

Successive delays saw Blackcomb pushed back to the end of the decade, with features progressively being jettisoned, (or "decoupled", in Redmondspeak) from Longhorn.

Microsoft shares fell 3 per cent in after hours trading on the news.

Now turn the page to remind yourself of five years of delays...