1. Try Safe Mode and see if you can download Malwarebytes.
2. Import Malwarebytes from a USB if that doesn't work.
3. Attempt to run. Instructions for helping to get it to run are on their forums.
4. Consider reformatting if this doesn't work, cause viruses nowadays are fucking annoying.
5. Ask for help on their forums because you won't get too far using any other tools on your own. Or, if you feel you are reasonably competent, try TDSSKiller or Combofix. Do anything stupid with those and you WILL be reformatting (since you can't restore to before using either). Both alter major files in the registry