Edit: %SystemRoot%\system32\drivers\etc\hosts
127.0.0.1 devads.skypeassets.net devapps.skype.net
127.0.0.1 qawww.skypeassets.net qaapi.skype.net
127.0.0.1 preads.skypeassets.net preapps.skype.net
127.0.0.1 static.skypeassets.com serving.plexop.net
127.0.0.1 preg.bforex.com ads1.msads.net
127.0.0.1 flex.msn.com apps.skype.com