I got these music videos that are in .wmv and .asf formats, and I wanted to know if I can make them any smaller, I always hear about DivX and Xvid encoding and how it makes files a lot smaller, so can you encode .wmv and .asf files in either of them?

ARRRGHH!!! <=Im a ninjapirate

You can but I wouldn't recommend it. Any reduction in file size will be offset by an equivalent drop in quality as they (windows media, divx, xvid) all use basically the same kind of compression (mpeg4).