I'm honestly quite surprised to see that Microsoft allows emulators on their store. You have to legally own a physical copy of the games that you have on your phone for the emulator. If you don't, it can be upward to an 80,000$ fine for game.
Not trying to be derogatory to the op or anyone here. Just stating the facts per U.S. law.
Sent from the stars...
They're allowing because they need apps on their store or WP8 may die, about this legal stuff, I don't know about others but is on my emu help FAQ page:
3) Its Legal to Copy a game I Own?
A: Yes. U.S. Copyright laws allow you to make one backup copy of software you own. However, that backup copy is “tied” to your original. If you sell or give away your original software, you must destroy your backup copy or package it with the orignal when you sell or give it away. Likewise, you may not sell or give away your backup copy without the original.
4) Its legal to download a copy of a game I own?
A: No. Even if you own the original game, you are not entitled to download a copy of it. Copyright law states that the only copy of software you are entitled to is the one you make yourself.
But remember that sony itself made the Xperia Play, with a built in PSX emulator.