How to install a new web browser
Makers of small web browsers want their programs to be given more prominence on Microsoft's browser choice screen.
Six software firms have complained to the EU saying many do not realise their programs were on offer.
To see all 12 web browsers, users must scroll to the right when viewing Microsoft's ballot screen.
The choice is being offered as part of a settlement of an anti-trust case brought against Microsoft by the European Commission.
"The final choice screen design leaves the vast majority of users unaware that there are more than five browsers to choose from," the six firms said in their petition.
The petition is signed by the makers of the Avant, Flock, Maxthon, Slim, Sleipnir and Green browsers. The makers of the other browser on offer, K-Meleon, did not sign it.
From 1 March, the browser choice have been popping up on the screens of millions of Europeans who have Internet Explorer as their default web browser.
The browser choice screen is designed as a single panel. Scrolling to the right reveals all twelve browsers on offer.
"We are only requesting the simple addition of any text or design element, that would indicate to an average user that there are choices 'to the right of the visible screen'," said the petition.
Microsoft said that the browser choice screen was drawn up to be compliant with the deal agreed with the European Commission.
Early reports suggest the browser choice screen is leading to a rise in the numbers of people trying browsers other than Internet Explorer.
In a statement, Opera said it had seen downloads of its browser increase threefold since the choice screen system started rolling out.
At the same time, the European Committee for Interoperable Systems (ECIS) has asked for the browser choice system to be repeated around the world.
In a statement it called on "competition agencies around the world to give their consumers the benefit of browser choice, which will spur competition and improve the Web experience for all".
So far, the ECIS campaign has got no further than an open letter on the organisation's site. However, it did not rule out a more active campaign on the issue of browser choice.
ECIS members include long-time Microsoft rivals Oracle, IBM, Red Hat, Opera and Adobe.