Bad news for Microsoft and Google – the two computer giants are bracing themselves for a hammering with the full force of EU regulations in the next few days, as privacy and anti-trust complaints against them finally come to a head.

Reports indicate that Microsoft is set to be handed a formal antitrust complaint by the EU, owing to its failure to comply with a 2009 agreement it reached with the European Commission (EC) to display a “browser choice screen” on Windows PCs. The EC states that since the agreement came into force, it has received numerous complaints that Microsoft has refused to provide a browser choice screen for all of its customers, which would give users the choice of using alternative browsers such as Google Chrome, Firefox, Safari or Opera alongside its own Internet Explorer.

Slightly unusually for a major corporation, Microsoft has responded rather meekly to the allegations, admitting that it had contravened the agreement in an estimated 28 million cases, owing to a technical error:

“We have fallen short in our responsibility to do this. While we have taken immediate steps to remedy this problem, we deeply regret that this error occurred and we apologize for it,” the company said in a statement.

But despite its sorrowful tone, Microsoft is unlikely to escape punishment for its lapse, with the EC Competition Commissioner Joaquin Almunia announcing that the software giant would face “serious consequences” for its failure to implement the agreement, with a fine potentially worth billions of dollars.

For its part, Google is also getting nervous that it too could be hit with a heavy punishment by the EU. UK newspaper The Guardian reports that CNIL, the French data protection agency, is to hold a press conference tomorrow when it will reveal the outcome of its investigation into Google’s controversial changes to its EU privacy policy that were introduced last March.

The Guardian claims that data protection chiefs have already determined that Google is in breach of EU regulations, as users were never given the chance to opt out of its new privacy agreement, something that directly contravenes European law.

Google’s privacy policy changes relate to its decision to merge the data it collects from its users from separate services – such as Google Search, Google Maps and YouTube – to facilitate more targeted advertising and video recommendations, depending on a user’s favorite search terms.

The web company is sticking to its line that its privacy policy still complies with EU law, but The Guardian believes that CNIL will insist that Google reverts and separates its user’s data once again.