pokesav doesnt get rid of your data, it edits it a little so that you can change it the way you want, no deletion is required
To use Pokesav
Put your Flashcart's SD card into an SD card reader and place into your computer
Open Pokesav
Click Open
find your Pokemon save game (for platinum, you need platinum's Pokesav, search the forums, link is here somewhere)
click on the things you wish to edit (you can even add pokemon to empty spaces)
click save
eject your SD card reader from your computer
place back into Flashcard
continue playing