Unfortunately, according to the official page Compass was not developed for Windows Vista, it works only with Windows 95, 98, Me, NT4, 2000, and XP. However, the last update was in September 2001, until now they updated this software without updating the information on the webpage. You can still take a look at Software Informer application's page; you are able to find there many other bookmark managers that work with Opera and also work with Windows Vista.
