If you downloaded your Vista from some P2P network, then i suggest you think twice before even starting the installation...
Vista Installation ISO is about 2GB (depending if it is Beta 1 or 2 but both of them are above GB) and so puting it on a um... CD, well, i wouldn't try it. Buy a DVD-Burner and have fun, or opposite.
if you want to download Vista from P2P so bad then just wait for Microsoft to release it. I promise you, no guarantee you that P2P's will be full of it.