IANAL, so talk to one if this information is of more than theoretical interest to you, but the Psystar case makes me believe it would not be legal. Courts seem to take a copy-centric view of things, so an illegal copy can only make more legal copies and a legal copy can only come from a legal copy.
So the pirate version would always be pirated in the judge's eyes, even if you had paid for a license for a legit copy as well. They won't let you use the legal license you acquired to cover a pirate copy. Or something like that, anyhow. There are always lots of funny little details that can make a big difference when dealing with law.
I'm not sure how applicable Psystar would be to an individual making a copy from an illegal one. Psystar was making copies of Mac OSX and then selling them. Even if it was buying licenses, it was making and selling copies. If this was one person doing it on their own PC, I'm not sure how different that is in the eyes of the law.
So the pirate version would always be pirated in the judge's eyes, even if you had paid for a license for a legit copy as well. They won't let you use the legal license you acquired to cover a pirate copy. Or something like that, anyhow. There are always lots of funny little details that can make a big difference when dealing with law.