PNG Help

I'm recently new to using PhotoShop more than every once in a while. I am learning very quickly and am using PhotoShop for web development but mostly for digital photo manipulation.

I have found a couple of PNG files that I thought would transparent but were not. How can I transform an existing png file that has been used to modify the boarder of pictures for rough edges..... The png file is not transparent and has a lot of internal noise/distortion that keeps the "magic wand tool from being able to clear out the middle are in one fail swoop?

If someone could help me I would be glad to email the file to you for additional help.

Thanks

ACEIII

If it is not transparent but does have a consistently colored background, e.g. white, you can go into the layer style properties and use the "Blend if" sliders on the General tab to drop away most of the white.

Use the top slider (This layer) and drag the little white triangle to the left until most of the background is gone, then press the alt key and drag again until you have nice smooth edges (no gunky crap).