The veiled threat was made in an annual report filing which Microsoft made to the Securities and Exchange Commission (SEC) on 25 August.
Meanwhile, four MEPs - one from Poland and three from each of the UK's main political parties - wrote to EU Competition Commissioner Neelie Kroes this week amplifying Microsoft's claim and warning that the EU's regulatory action against Microsoft will damage the competitiveness of European firms.
"This effectively means that the Commission's actions are endangering the ability of European business to compete globally," said the letter signed by Conservative MEP Chris Heaton-Harris, Liberal Democrat Sharon Bowles, Labour's Peter Skinner and Michal Kaminski from the right-leaning Law & Justice Party of Poland.
The four maintain that Europe's small and medium sized businesses will suffer from Vista's delay, but that this category of business is notoriously slow at adopting new technologies.
The Commission in March gave Microsoft chief executive Steve Ballmer a list of concerns it has about certain functions in Vista, and how compatible the OS would be with products from other software vendors.
Microsoft stated that it has replied and is awaiting a reply from the Commission to see whether product changes are required before it can release Vista in Europe.
The Commission argued that it is not up to them to give Microsoft a green light before Vista is released.
"It is up to Microsoft to accept and implement its responsibilities as a near-monopolist to ensure full compliance with EU competition rules," a spokesman said.
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