That exec file is for PC users only. Just delete!
As for the previews, if you're using my technique (discussed earlier) for preview pics attached to folders, the quality will vary with the resolution and size of the image you have copied for the preview. So, if it's a real small jpg image at 72 dpi, it will be blurry and not so great.
However, the previews that get attached to files automatically from Photoshop (check your preferences settings) should all look pretty great.