Hi armyers and welcome to the forum!
It's actually quite simple. In windows mail, just go to your contacts, highlight all the items there (or Ctrl+A), then right-click to select copy (or Ctrl+C) and paste it to a folder you created to store your backup
Now if you want to restore them back to windows mail, just reverse the process and there you have it, a simple solution to back up your contacts.
Alternative Solution: You can use Windows Easy transfer to backup all your mail, contacts, etc. This can be accessed by going to Start>All Programs>Accessories>System Tools>Windows Easy Transfer. You can configure what you want to include in the back up and its very user friendly.
Cheers