UK businesses could throw a cog as stocks of Microsoft Office 2000 run out.

Systems administrators trying to buy old versions of Office and Office 2000 Developer now have little choice but to buy Office XP, even if computers on their networks are running Office 2000.

The situation has been causing disruption at businesses in the UK and abroad as IT managers subject Office XP to rigorous testing to check its compatibility with Office 2000.

"It's all for revenue; this is Microsoft sticking the screws in," claimed one senior system administrator, who wished to remain anonymous.

Some IT professionals are angry that Microsoft has not given businesses enough time to adjust to the changeover between Office 2000 and Office XP, which was launched in the UK just seven months ago.

The only other option available to system administrators is to upgrade their entire networks to Office XP.

"When you have 2,000-plus PCs and hundreds of applications to worry about it is not a trivial exercise," said a London-based senior IT director.

But a spokeswoman for Microsoft said: "Office XP has been out for a long time now. Once a new version is released, that becomes the version we sell. If you can still get hold of previous versions, it's because old stock is left in the channel."

Microsoft Office XP was launched on 31 May last year, but until last month previous versions of the software were on sale.

Computer retailer Simply told PC Advisor that stocks of Office 2000 had run out and they were now only selling Office XP. But one disgruntled system administrator managed to buy a copy of Office 2000 from Simply as recently as late December.

The situation does not just affect UK businesses. A senior IT manager in the US told PC Advisor they had tried in vain to obtain Office 2000 Developer from four different retailers.

Microsoft has been criticised for recent changes to its business software licences, known as License 6.0 [sic]. Critics claim it is a way of pushing Microsoft customers on to a quick upgrade cycle.

But Mike Pryke-Smith, Office's head of marketing, claims that, under volume licensing, upgrading to Office XP works out at around £75 cheaper per copy than a standard purchase.

"We would recommended that all customer buying more than two to three copies should move to volume licensing," said Pryke-Smith, somewhat predictably.

A survey published by analyst IDC this month showed most business customers were either still evaluating License 6.0 or were not concerned with it, implying Microsoft still has some work to do persuading companies to migrate to its volume-licensing upgrade model.