I am not sure if everyone already knows this(I’m seeing so many of these threads) but there is a free alternative,
quixel tucked this away cleverly…
http://quixel.se/dev/ndo, scroll to the bottom of the page, you should notice “download nDO legacy”(same thing with ddo)
100% free
I personally think nDO is much better than crazy bump in creating normals
and ddo is much better than crazy bump in creating spec maps