Magnet links not loading from Internet browser with Windows XP :

In Windows XP you may have problems with magnets with a url length over ~2050
characters (crazy number of trackers put in the url...), when using in your browser
the internal windows association for magnet urls with your bittorrent client (not
only ABC_OKC).
The problem comes from the limit for the length of the command line in Windows XP.
Moreover if this limit is reached, Windows XP does not truncate the command line but
just outputs an error message without starting the command.

More recent Windows have a higher limit for the length of the command line.

With Windows XP nothing can be done in the bittorrent client.
You must try other ways of getting the torrent :
  - download or copy the magnet into the clipboard and use the clipboard scanner or
    paste it into "Add torrent from URL or info_hash"
  - If it's a public torrent and you have access to the info_hash, do the same with
    this info_hash
  - get the torrent file directly