how to convert mdf file to mpeg file?

MDF File is a CD image for alcohol120, itself cannot be convert to MPG unless its a VCD or DVD image

If its VCD image, then mount it to a virtual CD-ROM drive (make sure alcohol120 installed in your computer) and copy out the folder "MPEGAV", it contain the MPG file. and then you can use the video conversion software (TMPEGEnc, WINAVI, etc...) to convert it back to MPG.

If it's DVD Image, then you need to use a decrypter to decrypt the DVD to the hard disk, which is a VOB file, then you can use video conversion software convert back to MPG