That's great, but let's adress two things you should know.
First, DOSBox should be installed into its' own directory. There's no adverse results keeping it where you put it, but it can get annoying later on when you want to play other games using it.
Second, don't mount the game directory as your C drive - instead mount its' parent directory. In this case, rather than
mount c c:\games\simearth use
mount c c:\games . Again, it's a matter of long-term practicality (when you automate the mounting by placing the commands into the DOSBox config file) over immediate convenience.
Finally, you can also automate the mounting of directories and switching to the C drive by editing the DOSBox options file and putting these commands at the end. Whatever's placed there is automatically ran when DOSBox starts.