Ah, yes, Spud. That's come up here before:
I don't use D-Fend Reloaded, but the game works fine in ordinary DOSBox for me: unzip (and unrar) the game c:\whatever\spud, mount c:\whatever as C, and then start the game using START.BAT.
Note that the contents of the Zip file is a multipart RAR. That means that you have to manually extract all the files in the Zip file to some directory and then extract the .RAR file. If you're just opening the .RAR by double-clicking it in whatever Zip manager you're using, you won't get all the files.
But this is all beside the point. I'm afraid that the download presently available here doesn't actually include the second CD, such that there is in fact no apparent way to continue once you reach the end of the first CD. I've been meaning to do something about it, but as you can see it's been two years since someone last mentioned it.