UDIF stands for Universal Disk Image Format. It is used on Mac OS X for .dmg disk images. UDIF is a flat file format, and is the native image format for Mac OS X. Also it can be opened and decompressed by Magic ISO ... you can also use the freeware MagicDisk that i found on their site that is the easier virtual cd-dvd i found so far it even doesn't require a restart :D .