The European Union has begun an investigation to determine whether Microsoft is upholding pledges to curb anti-competitive practices.
It is consulting PC makers, software firms and consumers on Microsoft's offer to allow users to pick different browsers when they install Windows.
The bloc ruled in 2004 that Microsoft had abused its dominant market position by freezing out rivals.
It said Microsoft must let rivals' products run on its operating system.
"The commission will formally market test proposals made by Microsoft to address concerns regarding the tying of Internet Explorer to the Windows PC operating system," said the EU's competition commissioner Neelie Kroes.
"The preliminary view is that Microsoft's commitments would indeed address our concerns," she added.
"PC users should have an effective and unbiased choice between Internet Explorer and competing web browsers."
