I am using a Dell XPS 410 desktop, with Windows XP. It has recently become infected with a virus or Trojan, “c:\WINDOWS\systems32\kwinkmdt.exWin32:Downloader-1B[Trj]. It was discovered by Avast 4.7 Home Edition. I am notified by Avast at each start-up. Any recommendations on how to permanently remove this problem?