[logfromblammo]

H2O is probably the second, third, or fourth most common molecule in the observable universe. H2 is definitely the most common, and all you need is a good explosion from a CNO-cycle star (viz. heavier than 1.3 solar masses) to liberate all those fusion-catalyzing oxygen nuclei, and they readily combine with any H2 they may meet.

So in a stellar accretion disc, much of the water will end up inside the new star, and dissociate, but quite a lot of it will gather in the planets, moons, and comets. Europa, for example, has about 2 or 3 Earth-oceans worth of water. Uranus and Neptune likely have solid cores composed mainly of ices that include water ice.