If you wish to play Game Boy (.gb) files on your Windows Phone then download and install Purple Cherry Game Boy emulator on your Windows Phone-run handset. The emulator is available on Windows Marketplace at a price of US $1.29.
By installing this emulator on your Windows Phone, you can also play old portable games (like Tetris, Links Awakening, Metroid 2, and Pokémon Red) on your modern phone at one-tenth the size of the original Game Boy titles. As far as legalities, licensing, or copyright issues are concerned, experts feel that the gesture by Microsoft to allow this app to stay in the Windows Marketplace shows that they validate its existence and usage.
But, still you have to browse the legally grey areas of the Internet to procure the .gb files. Once safely downloaded, you can add them to Purple Cherry either by synching to your SkyDrive account or through public URL.
Visit the Windows Marketplace to download and install the Purple Cherry emulator on your Windows Phone device.