Brussels, 29/03/2006 (Agence Europe) - On Wednesday the Commission's spokesperson confirmed that Neelie Kroes, the Commissioner for Competition, had written to the CEO of Microsoft, Steve Balmer, requesting that he respect competition rules on his new Windows Vista programme. The letter, however, does not yet constitute the beginning of a formal investigation but a “simple warning”, he underlined. In her letter, the Commission points out that Microsoft had two obligations: ban on grouped sales and compulsory provision of sufficient technical documentation. The Commission warns the US giant that it will not be able to market Windows Vista in Europe if the user package was sold automatically with Microsoft's search engine and anti-virus. The Commission is concerned that the grouped sales of Vista with the search engine and/or anti-virus does not help Microsoft competitors but positively eliminates them from these sectors.