This procedure has been tested in Skype version 18.104.22.168 and proven working by the time this tutorial is being written. The information on how to disable Skype pop-up or start up ads was obtained from the Skype Community Forum. There is no complete assurance that this will work, or for how long this will work. This procedure is not officially from Skype but formulated by a Skype user so try at your own risk.
1. Click Tools >> Change Language >> Edit Skype Language File.
2. The Skype Language File Editor window will open.
3. Search for s_LANGUAGE_NAME (you can also just paste it in the Search box).
4. Double-click on the word English (under Current) and change its to SKYPE. Then Click OK.
You will be taken back to the Skype Language File Editor window, then click Apply.
5. Click the Save As button, the Save As window will appear then enter SkypeEnglish.lang in the File Name box. Click Save.
6. Close the Skype Language File Editor window. Then click Tools >> Change Language >> Load Skype Language File. Select SkypeEnglish.lang.
7. Restart Skype.