These are fully compatible icons for both OSX and Vista/win7 You can find the full download link for everypony below on Atomic Graymon's DA page!
And a quick how-to guide for Windows 7/Vista users
1. Download the .rar
2. Extract the .icl file
3. Toss it in your pony folder
4. Right click an icon on your desktop
5. Select Properties
6. Click the "shortcut" tab
7. Click "Change Icon"
8. Browse to your pony folder, select the .icl file
9. Choose Icon and Save As!