Seems like the MIME settings for the png files are whacked up...
Open up the registry editor ( regedit in the start menu search box)
Goto the HKEY_CLASSES_ROOT "folder" (see root.png)
You will have to do a little bit of scrolling but find .png "folder" in the ROOT "folder" (see png.png)
With it selected you see something like
on the right side of the editor.
Are the settings similar/the same as mine?
[recovering disk space, attachment deleted by admin]