Shareaza has a bug where it associate magnet links on Windows 10.. and even when unticking magnet link association in Shareaza settings, it still is associated. Windows 10 does not allow changing to other application.

Solution: i use Firefox web browser and in its Options/Applications, search for magnet and change default application from Shareaza to the app of your choice.

Solution2: uninstall Shareaza and use other P2P app for Gnutella, eDonkey. Not many are active:

Do you know about other solution to this?