Four more states have joined an effort to see that oversight of Microsoft's antitrust settlement continues another five years, until 2012. Previously, Florida, Louisiana, Maryland and New York were among a group of states that believed that Microsoft's antitrust settlement has had the desired effect. But now the states have joined the so-called California Group, arguing that Microsoft's anticompetitive behavior has continued.

According to the four states, Microsoft still controls over 90 percent of the personal computer OS market, and thus must still be monitored to ensure that it acts in the best interests of consumers and in a manner consistent with healthy competition. They join the California Group, which now includes the District of Columbia as well as six other states--California, Connecticut, Iowa, Kansas, Massachusetts and Minnesota--in requesting that US District Court Judge Colleen Kollar-Kotelly extend Microsoft's oversight period past its November expiration.

Microsoft was found guilty of abusing and illegally extending its desktop OS monopoly, but settled in 2002. Since then, the software giant has been closely watched by Kotelly and representatives of the US Department of Justice (DOJ) and the various US states that allied against it. The DOJ does not  believe that the California Group has met the standard for an extension of Microsoft's antitrust oversight, however.

Microsoft will issue a response to the California Group by October 30. The two sides will then appear before Kollar-Kotelly in November to debate the matter.