Photoshop :: How Do You Make Vista Icons?

I've been trying to make a icon for Vista (actually Windows 7 RC, but it uses the same guidelines) and simply cannot get it to work. I have my icon made in a 256x256 size and saved into .png. I edit the .xml file for my library that I want the icon to go for, but it simply changes it to the default folder icon. The XML coding is right, the location is correct, so it must lie within how I made the icon. Now, I know the default icon in the "Vista guideline" requires 256x256 and 11 other sizes; I had figured this would just downsize automatically. Do I resize the icon manually in seperate layers or what? And I apologize if this is the wrong place or this has been answered. I've searched the internet for at least 30 minutes, searched this forum lightly and came up empty. Also sorry if this seems more like a Windows issue rather than a Photoshop issue, but generally going into a Windows forum and asking this will get you a bunch of garbage, seeing as they may or may not have experience with making icons. P.S. The PNG is not interlaced;