Despite growing pressure from Linux, Microsoft's Windows gained an even greater share of the server operating-system market last year, according to data released Oct. 8 by market researcher IDC.

Windows accounted for 55.1% of the worldwide server market in 2002, up from 50.5% in 2001, IDC says. Linux garnered 23.1% of the market, compared to 22.4% a year earlier. The 2002 percentages represent each platform's respective share of 5.7 million new server licenses that shipped.

Windows and Linux grew at the expense of other operating environments. Unix variants got 11% of the market in 2002, NetWare 9.9%, and other operating systems slightly less than 1%.

Windows also notched up in share of client operating systems, with 93.8% of the desktop market in 2002, compared to 93.2% in 2001. Mac OS and Linux each had almost 3% of what remained.

Overall, the number of paid server licenses jumped 9.6% last year, while paid client licenses grew 5.1%. IDC pegs the server market at $18.6 billion. The numbers include only commercial distributions of Linux, not free downloads.

IDC expects the trends to continue, predicting Windows and Linux shipments will continue growing through 2007.