Microsoft Corp. late today fired off a return legal salvo at Google Inc., and filed a memorandum with a federal judge arguing that its rival should not be allowed to intervene in the antitrust case settled in 2002.

Earlier Monday, Google submitted a request to file an amicus curiae, or "friend of the court," brief with Judge Colleen Kollar-Kotelly, who oversees the consent decree between federal and state regulators on one side, and Microsoft on the other. In the brief, Google said that last week's deal over changes to Windows Vista's desktop search didn't go far enough, and it asked the judge to extend her oversight to make sure Microsoft made good on its promises.

Hours later, Microsoft contended that Google has no standing in the case, and so should not be allowed to join the settlement discussion. "Google has nothing new to offer the Court, except for the veiled request that this Court go behind the enforcement decision of the plaintiffs and make Google the '20th Plaintiff'," Microsoft's seven-page memo read.

Also in the memo, Microsoft attempted to undercut Google's reason for extending the consent decree by promising to release a beta Vista Service Pack 1 (SP1) before the decree's Nov. 12 expiration. Google had hinted that Microsoft, which had previously committed to launching SP1 only before the end of the year, might never implement the changes. The Nov. 12 deadline for Vista SP1 is the firmest timetable yet for any major milestone of the update.