Trojan.Zeroaccess!inf4: HELP please!

Since I updated my Adobe Flashplayer, my PC started acting very strange: loss of focus in programs, a lot of hard disk activity, WiFi no longer responding... Then my Symantec Endpoint Protection discovered the Trojan.Zeroaccess!inf4 in Services.exe, but it's unable to remove it: I've tried everything I possibly could, but no results. Can anyone help me out?