There is a registry tweak which you need to apply to stop previews, but considering that searching for it and getting it is a lengthy task at the moment, here's a work-around suggestion:

1. Go to some other folder which has like 2 images in preview mode.
2. Right-click and set: View - as icons
3. Now go to "Folder Options", and in the "View" tab, click "Apply to all folders".

Do post back on how it goes. Hoping this helps....