Microsoft continues to give its tacit blessing for consumers to exploit a technical loophole that allows them to upgrade to Vista with Service Pack 1, even if they don't own the necessary prior editions of Windows. The loophole, which was also present when Vista was first released last year, allows individuals undaunted by Microsoft's licensing and installation rules to save up to $110 by purchasing a DVD upgrade of Vista SP1, rather than the full retail one. To install an upgrade version of Vista, users are supposed to have Windows 2000 or XP already running on that computer. Experts say Microsoft is giving its quiet blessing to the loophole in order to boost interest in Vista among the tech-savvy users likely to exploit it.

Vista SP1 became available via retailers such as Amazon.com several weeks ago. The upgrade version of Vista Home Premium SP1 costs about $130, versus $239 for the full edition, though Amazon.com is temporarily offering them for $90 and $205, respectively. Similarly, Vista Business SP1 lists for $299 and $199 for full and upgrade versions, while Vista Ultimate SP1 lists for about $320 and $220.