Following "How to Load .img Files Into MapSource ..." Have .dtb file, so using "Install a existing Mapset" box. When clicking INSTALL, get Family ID exists error box. What is wrong?
Sounds like there is a mapset using that family ID already installed in MapSource.
Which map set are you trying to install and what is already installed in MapSource?
Yes, it does appear that there is another map installed with the California Topo name. In following the tutorial, I downloaded cgpsmapper.com and it created a California Topo name. I suppose it needs to be removed but I don't know how to do that. I want to add the downloaded California Topo. Gosh, I was going so well up to the very last step. So I guess I don't need to use cgpsmapper? Thanks.
Use MapSetToolKit - it will show which mapsets are installed in MapSource and allow you to uninstall. Do not uninstall those which came with MapSource.