Yes they two technologies are totally different. DVD or Digital Versatile Disks are the newer ones that hold more data and are usually read by all the usual DVD rom drives... however VCD's (or Video CD's) are totally different. Even the disk is different for that matter (i.e. it's a CD). However you should be able to play any VCD on any regular CD/ DVD-Rom drive.
The problem probably is that you aren't using a proper player (well to be specific it probably doesn't have the codecs to do is since VCD's might be slow, or the ability to decode VCD's werent' in the player that you are using) to play the VCD.
The solution probably would be using something like Quick VCD
(I haven't tried this out though..) or something like that.