File shredder

My old laptop used Avast Premier and occasionally I would shred deleted data. When I commanded Avast to shred all deleted files it would automatically delete the C drive, the main drive. I now have a new laptop and I have a C drive, D drive and E (Recovery) drive. Now, when I command Avast to shred all deleted folders it only shows the D and E drive as options. Does anybody know why I can no longer shred temp and deleted folders from the C drive or how can I set up Avast to shred from C drive?

Repair Avast:

  1. Control Panel → Add/Remove programs → Avast
  2. Click on ‘Repair’.
  3. Follow instructions.
  4. Reboot.