Windows XP and Vista users will be given a choice by Microsoft as to whether they want to install Internet Explorer or one of its many rival browsers.
On July 24, Microsoft published a proposal it had sent to the European Commission, saying it could alleviate antitrust fears by giving european users of Windows 7 a choice of browser first installation.
However, the proposal also suggested giving XP and Vista users the same option, via Windows Update:

For Windows XP and Windows Vista users the Ballot Screen update will first be made available between 3 and 6 months after the adoption of the Commission's decision under Article 9 of Regulation 1/2003. For Windows 7, the Ballot Screen update will first be made available to users by the date of the general commercial release of Windows 7, or within two weeks of the adoption of the Commission's decision under Article 9 of Regulation 1/2003, whichever comes later.

Each browser listed on the ballot screen would come with two links: one for direct installation and one for further information. "The Ballot Screen software update will be distributed and installable via Windows Update in a manner that is designed to bring about installation of this update at a rate that is as least as high as that for the most recent version of Internet Explorer offered via Windows Update," the proposal added.
Microsoft may offer tools to volume license users to stop the ballot screen being installed on PCs covered by the license, while still allowing standard manual installation of rival browsers on those PCs, the proposal stated.