Hello Colleen.
Unless you are using a Tile Server or some sort, only one image is loaded at a time. I presume the one image you are seeing is the last one in the loop. And yes, it should use the World file to help position the image.
Theoretically, MWGis supports the MrSid file format (although I’ve never tried it). Have you tried that? I believe you have to specify when installing the OCX that you want MrSid support (it may not be installed by default).
I’ll have to look into the ECW issue that you make mention of. I don’t know the status off-hand.
Jerry.