They look pretty good at 256x256, but you might want to create a new png from scratch at somewhere between 72x72 and 48x48 in order to preserve the detail. The reason I say this is that you have several paces on both icons where you have light/medium/dark bands very close to each other, like around the edge of the CD image, for example. Depending on which program you use, (Microangelo, Axialis IW, Stardock IconDeveloper, etc.) the algorithm they use to resize the image all work on some method of averaging the color of adjacent pixels. What you will find is that that neat 3d effect you have with nice thin lines is going to get fuzzier and lighter as the image is resized smaller. You can touch up the individual icons after resizing, but sometimes it is easier just to make a new image from scratch at a smaller size and then resize that to get the smaller images. On your Word DOC image, I'm afraid you may have the same result on the gray D and the gray part of the O. I would suggest trying to run them through whatever icon creator/converter you're planning to use and see what happens. I'm just trying to relate what I've discovered so far, as I'm still learning the process myself.

I am going to use fireworks ( I created them in Firewoks) to make them smaller by scalign them to the correct sixe. It should work well becuase they are vetors. I will change things if need arises