Microsoft shares soared to their highest level in six years after first-quarter sales beat projections by more than $1 billion, proving the new version of Windows has reinvigorated growth.

Microsoft, the world's largest software maker, rose the most in seven years on the Nasdaq stock market. The shares advanced $3.87, or 12 per cent, to $35.86 at 12:01pm, the highest since July 2001.

Sales of Windows Vista for personal computers climbed 25 per cent, helping chief executive Steve Ballmer reassure investors who had been disappointed by the operating system's lacklustre early adoption.

The stock had lagged rivals this year and the report allayed concern that Microsoft's growth depends on cracking Google's dominance in internet advertising.

"This is a big deal," said Jane Snorek, a Minneapolis-based analyst at First American Funds, which manages $55 billion in assets, including Microsoft shares. "It will change the sentiment on Microsoft absolutely."

Net income increased 23 per cent to $4.29 billion, or 45 cents a share, beating the 39-cent average of 15 projections in a survey by Bloomberg.

Sales advanced 27 per cent to $13.8 billion, driven by orders for the pricier versions of Vista and the debut of the Halo 3 video game. - (Bloomberg)