Microsoft, the Goliath of the software industry, has announced it will allow computer makers and users to set other firms' applications as defaults.
Microsoft is opening up in many ways, the firm says
The change is one of a dozen "tenets to promote competition" that senior VP Brad Smith announced on Wednesday.
But the principles are not designed to address all of the European Union's anti-trust concerns, he said.
And they will not delay shipping of Microsoft's new Vista operating system, planned for January 2007, he promised.
"The principles don't affect the launch date or the shipping schedule," he told the BBC.
Vista has already been pushed back from late 2006 to early 2007 - after the crucial Christmas sales period.
Key US lawmakers welcomed the software giant's competition announcement.
But it is not clear that it will satisfy the European Commission, which has been Microsoft's toughest critic when it comes to competition regulations.
The EC has fined Microsoft 280.5m euros ($357m; £194m) and threatened it with new fines of 3m euros a day for failing to comply with an anti-competition ruling.
Microsoft cannot act as it once did, Mr Smith said
Microsoft is appealing against the decision and Mr Smith said the Redmond-based firm had met its deadline to submit paperwork related to the case.
"We handed over 2,600 pages of new technical documents yesterday. We have produced over 8,000 pages in the last two months," he said, adding that the EC trustee in the case would give the company feedback on them.
He also pointed out that the EC was concerned about server issues, while Wednesday's announcement was about desktop applications.
The fine dates from a landmark EU ruling in 2004, which ordered the US firm to provide rivals with information about its Windows operating system.
The 12 newly-announced principles may go some way towards satisfying the critics.
- Allowing computer manufacturers to set defaults as they wish, instead of exclusively to Microsoft applications
- Giving outside software developers the same access to technical information that Windows developers have, so "competitors will know that they can plug into Windows to get services in the same way that built-in Windows features do"
- Promising not to retaliate against computer makers that support non-Microsoft software.
The principles might mean that some manufacturers will promote search engines other than Microsoft's own, Mr Smith said - an apparent reference to Google, which has looked to be on a collision course with Microsoft over search engines.
"There are certain steps we can't take that would have been permitted a decade ago," the executive added.
But he said he was confident of the company's ability to compete.
"We've got to offer a great value product, especially to consumers. If we do, I would hope we'll be successful."