Tyrphanax said:

Well, at the time Anakin was becoming Vader, one of the Death Stars was already under construction, and if you take the EU into account, there was already a prototype completed at The Maw, so he would have had access to those right off the bat at very least.

The death star at the end of episode 3 was a prototype.

Also, the Maw death star that U R talking about, that was during episode 4 A New Hope. I looked it up on wookipedia, if he defeated emperor palpatine at the end of episode 3, then the maw death star prototype wouldn't have existed, therefore your arguement that Emperor Darth Vader would've used it is invalid and false, no offense intended here, bro.......

Well, if darth Vader defeated the emperor at the end of episode 5, well, then maybe, maybe not......