These icons are provided by Icojoy.com.

They are part of tutorials provided by Icojoy to teach you how to make glossy buttons. 

Here is the tutorial for the Mac Style buttons.

Here is the tutorial for the Vista Style buttons.

I included a flattened .png version of the buttons with transparency in case you don't own a copy of Photoshop.

After writing to Icojoy to see if i could post them on OGA, they responded:

The vista and aqua buttons tutorials are copyrighted by Icojoy, you
can post these articles anywhere if you post a backlink to
www.icojoy.com. The icon sources in this tutorials are free to use in
any kind of commercial or non-commercial project.