I always tend to think it will be under Tools->Folder Options but it is actually under Advanced System Settings.
To change it...
- Press Windows Key+Break to bring up the system window,?
- In the left pane, select Advanced system settings
- Go to the Advanced tab and select Settings in the Performance Groupbox.?
- Check the "Show thumbnails instead of icons" thumbnail
Just thought I would put it here so I can find it next time easier.?