Microsoft has filed motions to dismiss the class-action lawsuit concerning its Vista Capable marketing campaign.

Lawyers for the company have asked US District Court Judge Marsha Pechman to decertify the class-action status so that people would have to sue Microsoft individually, and to dismiss this particular case.

"The evidence refutes plaintiffs' claims that Windows Vista Home Basic cannot 'fairly' be called Windows Vista," Microsoft said.

"Windows Vista Home Basic has nearly all of the same computer code as the rest of the Windows Vista family and ... Microsoft never publicly defined Windows Vista in a way that would exclude Windows Vista Home Basic."

The case was brought after Microsoft delayed the launch of Vista until after the crucial Christmas sales period, and came up with a campaign to let consumers identify PCs that were 'Vista Capable' or 'Vista Ready'.

Some people who bought 'Vista Capable' machines found that they could only run Vista Home Basic, which the lawsuit contends offers very little difference to Windows XP.

As part of the background for the case emails have been found that show deep disquiet about the campaign within Microsoft, and with external partners such as HP.