[How can I remove the background in this picture without affect other parts?]

You could use this;  http://forums.getpaint.net/index.php?/topic/26966-trs-alpha-cutter-v304-april-7th-2014/

Looks good, but I'm not sure how to install it. Also, do you know if it works with version 4 of Paint.NET?

[How can I remove the background in this picture without affect other parts?]

   I want to remove everything but the card. I tried using the magic wand but it keeps selecting parts of the card. I am very new to Paint.NET

[paint.net 4.0 is now available!]

Awesome! I just started using Paint.net a few days ago.