Not sure how it works in older versions, but in Firefox 3 RC2, the search engine you choose seems to persist across instances of the browser. So select Yahoo on

Not sure how it works in older versions, but in Firefox 3 RC2, the search engine you choose seems to persist across instances of the browser. So select Yahoo once and it stays Yahoo (unless that resets on a system restart). There is a link to adding search engines on the Manage Search Engines window that pops up. I'm not sure why complicating the install process with silly details like this would be a good thing.