The European Union (EU) has written to Microsoft to state its anti-competition concerns about the US giant's new operating system.
Neelie Kroes wants more information from Microsoft
EU Competition Commissioner Neelie Kroes is worried that the forthcoming Windows Vista system will not offer customers a real software choice.
Yet the letter does not mean the start of a formal inquiry, and Ms Kroes is responding to a query from Microsoft.
Microsoft had asked EU regulators to set out any Vista concerns it may have.
"We're concerned about the possibility that the next Vista operating system will include various elements which are currently available separately either from Microsoft or other companies," said EU competition spokesman Jonathan Todd.
Microsoft has delayed the main Vista launch until next year
He added that Ms Kroes and her department were highlighting Vista's integrated internet search, digital rights management and documents software as key areas of concern.
"We assume that Microsoft has its own interests at heart," said Mr Todd.
"It wants to launch another product without having to worry about the Commission instituting various actions under anti-trust law."
The EU's look at Vista is entirely separate from its continuing legal dispute with Microsoft over Brussels' 2004 anti-competition ruling against the US giant.
Brussels has since accused Microsoft of dragging its feet over implementing its call for the firm to open up its software systems to rivals - something Microsoft denies.
Delays mean the launch of the main consumer version of Vista will not now take place until early next year.