I had approximately 200 tabs grouped in approximately 30 groups in Firefox 31.0 (latest version). The grouping showed up when I clicked the icon on the left of the "minimize" button or pressed CTRL+SHIFT+E. It is called "Firefox - Group Your Tabs". I also use Xmarks, but I turned off tab synchronization recently. Usually all the tabs and their groups were saved when I closed Firefox. Today I opened Firefox and all the tabs and groups were gone! Instead there opens some search engine called Trovi (www.trovi.com) with "Results by bing". Its the same in Chrome, Opera and IE. My OS is Windows 8.1 Update 1 with all updates installed. My antivirus is Avast! with all updates installed. There must have been some malware installed obviously, but I didnt get any alert. I have run a "Complete system test" in Avast! with latest updates, which is the most in-depth scan I know (without restaring my laptop HP ProBook 4730s). No virus has been found. I am suspecting a program called "Search Protect" version 2.16.10.61 from "Client Connect LTD". It has been installed along with PowerISO 6.0 x64. I tried to run System Restore, but it seems all the restore points I have ever created are deleted now! I discovered this by opening System Properties -> System Protection -> System Restore. However "Protection" is "On" for my system drive. How can I restore my tabs and groups? It is extremely important to me.