I have a MPEG2 video file without embedded audio. Audio is a seperate AIFF file. I need to make a MP4 video file with embedded audio.

Is there any way I can embed the AIFF with the MPEG2 and make a MP4 output??

YAMB + MP4BOX.

...but why MP4? MPEG-2 accepts PCM too, and has wider hardware support.

If you have the mpeg2 codec for quicktime pro, I thought if you open the video it opens with audio (even though they are seperate files). I might be wrong though.

If you have the mpeg2 codec for quicktime pro, I thought if you open the video it opens with audio (even though they are seperate files). I might be wrong though.

This can also be done wit MPEG streamclip with the free Perian plug-in for Mac or the free Quicktime Alternative for PC.

On the PC side, convert the AIFF to a WAV file (there are numerous free tools to do this) then load the MPEG2 and the WAV into VirtualDub-MPEG2 to make a DixV or XviD AVI (provided the codecs are installed)

You can keep the whole thing in MPEG-2. No recoding, and the result will be playable in any DVD player (PCM is a mandated codec right?).