Is it possible to CHOOSE which image is the thumbnail preview picture?

I love cutomising my pictures libraries & in previous version of windows it has let me select which image becomes the preview on the thumbnail by following options via Properties>Customise.

Since I've had windows 7 I can find no option to allow me to select myself which image appears on the folder thumbnail! Has this feature been removed or am i just being really thick & not finding it anywhere?

Any help would be great, thanks very much! :)
Fi xxx

rename the chosen picture "folder" without quotes. there you go:)
cheers

thanks so much! :) i order all my pictures by name so ive just copied the one i like, done as you said then hid it! thanks so much for your help!! xxxxx

You are welcome:)
cheers