European Competition Commissioner Neelie Kroes has said she expects heavy fines against Microsoft for breaching competition rules to come into force.
Microsoft insists it has complied with the EU's competition ruling
Ms Kroes said she "could not imagine" any other outcome in the legal wrangle between the EU and the software giant.
Microsoft faces daily fines of up to 2m euros ($2.4m; £1.4m), following an EU anti-competition ruling in 2004.
The US firm insists it has met EU demands to make its software work better with that of its rivals.
Ms Kroes said EU member states broadly supported the European Commission's threat to impose fines against Microsoft.
Earlier in the week, an EU committee ruled that Microsoft had failed to comply fully with the Commission's original anti-competition ruling in 2004.
Under that ruling, Microsoft was told to provide rival firms with more information about its software, in order to enable them to write programs that could run more smoothly on Microsoft's widely-used Windows operating system.
The judgment also called for Microsoft to debundle its Windows Media Player from its Windows operating system, and hit the software firm with a record fine of 497m euros.
European regulators are expected to meet on Monday to decide the size of the daily fine which Microsoft will be ordered to pay.