I think that VCD 1.0 has a MPEG file on the CD that you can just take off.
However, VCD 2.0 has some more myseterious files. The one in the "MPEGAV" folder (can't remember what its called, but it is .DAT and it will definately be the largest file on the CD... and there'll be more than one if the CD has more than one "Chapter") is the actual movie, and it is encoded in MPEG (MPEG-4, I think), so it should be rather easy to convert it to an MPEG.
HOWEVER - the only programs I can find that mess with VCD 2.0 are Roxio Easy CD Creator 5 (to make them) and WinDVD 3.0 (to play them). None of the freeware VCD players on the internet seem to play VCD 2.0. I have not yet tried to convert one to MPEG...