Microsoft has started pushing automatic updates of Internet Explorer 7 to all English users of Windows.

The updated browser is Microsoft's answer to the growing power of open-source browser Firefox in a market where the software giant has held a virtual monopoly for a decade.

That the browser - which makes significant changes to Windows' underlying architecture - has been pushed through the system that Microsoft uses for security patches has raised eyebrows, but the company has sought to avoid criticism by stressing the new version's security advances and by forcing users to accept installation before Explorer 7 is put onto their machine.

Microsoft is also rolling the change out slowly, starting a few days ago, said Explorer's director of product management Gary Schare. "On Wednesday of this week, we began a very slow distribution through automatic updates, throttled way down so a very few users would see it."

Microsoft has been sending the updates to one percent of English language Explorer 6 users - about one million PCs - per day.

The whole process is likely to take three months although Share wants to move faster. "We'd like to get the software out to as many people as quickly as possible, because we think there's a lot of security value," he said.

The pace of the rollout has been kept purposefully low to prevent Microsoft's technical support center from being overwhelmed, and to prevent administrators who are not blocking the update from being crushed with software updates next week when Microsoft will release six sets of security patches. "We keep the Explorer throttle low, so when the security updates come out next Tuesday, they still have priority," he said.

To date the IE 7 updates have been going "quite smooth", Share said. Though the automatic updates are sent without any interaction from the Windows user, the software asks customers whether they want to install Explorer 7 before proceeding with the installation.

European and Arabic-speaking users should begin to see automatic updates in the next few weeks, with German, French, Spanish, Brazilian and Arabic versions after that. The last versions to be distributed will be the Japanese, Korean, Chinese and Hebrew versions of the browsers.

Original reporting by IDG News Service