Steps to block Skype ads (requires Windows Admin)
NOTE: Will render "Skype Home" unavailable. Skype home is not required for full Skype functionality.
1: Run cmd.exe as Administrator
2: Type: notepad %windir%\System32\drivers\etc\hosts
3: Add this to the end of the file
#Block Skype ads
127.0.0.1 ds.serving-sys.com
127.0.0.1 speed-s.pointroll.com
127.0.0.1 rad.msn.com
127.0.0.1 g.msn.com
127.0.0.1 live.rads.msn.com
127.0.0.1 ads1.msn.com
127.0.0.1 static.2mdn.net
127.0.0.1 ads2.msads.net
127.0.0.1 a.ads2.msads.net
127.0.0.1 b.ads2.msads.net
127.0.0.1 ad.doubleclick.net
127.0.0.1 ac3.msn.com
127.0.0.1 ec.atdmt.com
127.0.0.1 msntest.serving-sys.com
127.0.0.1 sO.2mdn.net
127.0.0.1 aka-cdn-ns.adtech.de
127.0.0.1 secure.flashtalking.com
127.0.0.1 cdn.atdmt.com
127.0.0.1 apps.skype.com