I love the cliparts too, Microsoft doesn't have very clear copyright items about them. But if you don't primarily use them in your publication, not resell them, also don't use them as a part of your logo, you should be fine. But please note that this is not legal advice.

You can find the official license agreement here, pay close attention to section 1.2.

By the way, I still don't know how to convert them into GIF files besides screen copy.