The European Commission has advised Microsoft that it has begun proceedings to investigate whether or not it has complied with an earlier anti-trust ruling.
If found guilty, the tech giant could face a fine of up to 10 per cent of its annual turnover.
In 2009, the Commission issued a Statement of Objections against Microsoft, claiming the company had abused its dominant position in the market by tying its Internet Explorer (IE) web browser to the Windows operating system.
The Commission said it was concerned that "given Microsoft's dominance of the PC operating system market, this deprives consumers of choice and results in fewer innovative products on the market".
Millions of Windows users in the EU may not have seen the browser choice screen.
Microsoft sought to remedy this by setting up a ballot screen' that enabled users to choose their preferred internet browser, rather than being automatically led to IE.
However, the Commission has taken the preliminary view that the organisation failed to roll out the browser choice screen with its Windows 7 Service Pack 1.
"From February 2011 until July 2012, millions of Windows users in the EU may not have seen the choice screen," the Commission said.
In response, Microsoft said: "We take this matter very seriously and moved quickly to address this problem as soon as we became aware of it.
"In addition, after discussions with the Commission, we are changing some aspects of the way the Browser Choice Screen works on Windows 8 and will have those changes implemented when Windows 8 launches," the firm added.
