Uncompressed AVI files can be extremely large. To reduce the size you will need to use some compression.
Huffyuv codec will give you a lossless compression of about 2.5 to 1
PicVideo codec can give to 5 to 20 to 1 compression
DivX 4.x can give you about 40 to 1 compression.
The one to use depends on what you want to do with the final AVI file and your HD space, etc.