Microsoft Windows 2000 remains one of the most widely deployed operating systems in corporate IT environments, despite the fact that mainstream support for the software is set to expire on 30 June 2005.

The operating system has entrenched itself in large enterprises, according to new research from IT business intelligence firm AssetMetrix Research Labs, losing only four percentage points in popularity from 52 per cent in the fourth quarter of 2003 to 48 per cent in first quarter of 2005.

The report also found that, while Windows XP is now the most popular operating system for companies with fewer than 250 PCs, Windows 2000 still has a greater than 50 per cent market share in larger organisations.

During the period covered by the research Windows XP rose in popularity from 6.6 per cent to 38 per cent.

The study also found that, within the same time period, Windows 95 and Windows
98 were reduced from a collective 28 per cent installed base to less than five per cent, while Windows NT declined from 13.5 per cent to about 10 per cent.

"The findings of this study suggest that Windows 2000 still plays an important part in many IT environments, with organisations often choosing Windows XP to replace Windows 98 and Windows 95," said Steve O'Halloran, managing director at AssetMetrix Research Labs.

"Companies redeploying PCs without a policy to manage and support their operating systems will have their Windows XP transition rate dictated by PC obsolescence rather than by intelligent planning and forecasting."