The current version of Windows Media Player will play AIFF files, but I don't know if there is a remote app for WMP to use on a cell phone.
The most important thing for making the transition will be for your audio files to be on a medium that can be read by Windows - not the standard Macintosh file format. I suggest backing up your audio files on DVD or on an external drive that has been formatted in a Windows compatible format. The Mac can format a drive as MSDOS(FAT) or ExFAT using Disk Utility, and you will be able to save files to a disk formatted this way.
The most important thing for making the transition will be for your audio files to be on a medium that can be read by Windows - not the standard Macintosh file format. I suggest backing up your audio files on DVD or on an external drive that has been formatted in a Windows compatible format. The Mac can format a drive as MSDOS(FAT) or ExFAT using Disk Utility, and you will be able to save files to a disk formatted this way.