This could be an undisclosed bundle feature from some software you installed recently... Could you start by checking your extensions? I suggest disabling ALL nonessential or unrecognized extensions on the Add-ons page. Either: * Ctrl+Shift+a * orange Firefox button (or Tools menu) > Add-ons In the left column, click Extensions. Then, if in doubt, disable. Before using any restart links that might appear, please check for a user.js file in your settings. Firefox reads this file at startup and it may override your settings changes. This article describes how to track down and remove the file: [[How to fix preferences that won't save]]. ''Note: If Windows hides .js and other file extensions, you can turn on the display of file extensions (so you can work with files more accurately) using the steps in this article: [http://support.microsoft.com/kb/865219].'' Then restart Firefox and see whether it behaves better. ---- To complete the cleanup process, I suggest: * Open Windows Control Panel > Add/Remove Programs, and click the "Installed on" column heading to group additions by date. This can be helpful in finding and removing unwanted bundled items. * Run some additional scanners to supplement your regular security software. This article lists tools other Firefox users have found helpful: [[Troubleshoot Firefox issues caused by malware]]. Any luck?