I noticed the other day that on one of my servers image thumbnails were not showing.

This is easy to fix, do the following:

1. Click Start  and Right-Click on “Computer” and choose “Properties”, (or if like me you like your “Computer” icon on your desktop then just Right-Click on the computer icon on your desktop).
2. Under “Tasks” on the left hand list of options click “Advanced System Settings”
3. On the “Advanced” tab, in the “Performance” group, click “Settings”
4. On the “Visual Effects” tab find and tick the following option “Show thumbnails instead of icons”
5. Click Ok
6. Click Ok

You should now be able to browse your images as thumbnails again.

Sigh! Thanks for turning that off by default Microsoft!