Intro: How to Make Your R4 Boot Any .nds File From the Second Icon on the Menu!
This will show you how to make your R4's second icon on the menu boot any .nds you want.
Step 1: Renaming
This is really simple to do. Delete the " _DS_MSHL.nds " file.
Copy and paste the .nds file you want to be booted, and rename to "_DS_MSHL.nds".
For mine, I used Licks Media Player (iPod clone).