you just have to reinstall system.
2. Check the DLL viruses using process embedded technology which hides the process
So far, there are some advanced viruses or Trojans, which use process embedded technology. They hide the process and embed DLL file to the current system processes, some common ones are embedd in explorer.exe and winlogon.exe. So far there’s rare antivirus software having good effect on killing the dynamic link library viruses. Sometimes antivirus software would even make a wrong judgment, such as the event that “Symantec kills two key system DLL files by mistake”.
  For the DLL files embedded in explorer.exe, mostly would use tool IceSword’s “Module/Remove” function to uninstall DLL file, and then manually delete DLL virus file.
  For the DLL files embedded in winlogon.exe, little part of them could be uninstalled by the tool IceSword’s “Module/Uninstall” function, and then manually delete DLL virus files; mostly you have no way to remove them.
 For the two situations you cannot “Remove” above, we need to delete the DLL virus files manually under safe-mode.
Besides, now there are many viruses or Trojans somehow may infect U disk. And Autorun.inf file and relevant EXE files would form on U disk.