Latest SKYPE update gives: An error occurred while applying security settings. Users is not a valid user group....

Re: An error occurred while applying security settings. Users is not a valid user group. This could be a problem with the package, or a problem connecting to a domain controller on the network. Check your network connection adn click Retry or Cancel to end the install... Due to this, installation is not complete and then when I try to change something in the video settings, the SKYPE program crashes each time. My Windows is XP Professional I am a non-technical user. (and don't have the password of the Administrator of my PC) So please give answers step by step, as I would see it on the screen... Thank you