WMF Thumbnails

Since moving up to Vista I see there is no Thumbnails option in the Folders
View section. I have hundreds of files with the WMF extension which I cannot
view 'on mass'. I have to use a program to view them individually which isn't
practical.

I have tried all the recommendations within the discussion groups which
describe how to view thumbnails without any success. I'm sure I read
somewhere this is a known problem as Microsoft considered these files a
security threat. Can anyone throw any light on this please.