The lawsuit, last Wednesday, stems from the $59.25 fee that a California woman was charged in mid-2008 when she bought a Lenovo laptop and downgraded from Vista to XP.

"Microsoft does not charge or receive any additional royalty if a customer exercises those [downgrade] rights," said Microsoft spokesman David Bowermaster in an e-mail late last week. "Some customers may choose or need to obtain media or installation services from third parties to install the downgrade version."

In fact, it's computer makers, not Microsoft per se, who charge users the additional fees for downgrading a new PC from Vista to XP at the factory. , for example, adds an extra $20 to the price to downgrade a PC.

Microsoft, however, may profit from the way it structures downgrade rights. Only buyers of PCs with pre-installed editions of Vista Business and Vista Ultimate can downgrade, and then only to Windows . All three editions are higher-priced versions of their respective lines, a fact that the lawsuit mentioned in passing.

"Customers have been forced to purchase the most expensive version of [Windows XP] in order to 'downgrade' from the Windows Vista operating system," the complaint read.