As I am not familiar with these programs, you'll have to work this one out yourself.
As a suggestion, I would create two folders on the new external hard drive - label one Videos, and the other, Pictures.
Then navigate to where your current files are (my best guess would be in the My Documents folder somewhere), select them all and, from the Edit menu, select Cut.
Then navigate to the new folder (on the external hard drive), and select, from the Edit menu, Paste.
You will need to do this once for each folder - Pictures and Videos. (And any other documents or files you wish to transport over).
Then you will need to open the programs, Kodak and Image Mixer, and see if they still work. You may need to "direct" the program to find the new location of your pictures and videos.
Perhaps somebody with more experience using these programs, will reply for you.