Thanks very much alanrochester for your help, I now have a better understanding of the ways SW are installed in Linux environment. However when I tried to have the SW XVidcap from http://linuxappfinder.com/ installed using the default GDebi package installer, I got the error message:" Dependency is not satisfiable", and when I tried another version of XVidcap, I got the error message: "A later version is available in a software channel. You are strongly advised to install the version from the software channel, since it is usually better supported." My question is where can I find this software channel? and what can I do with the dependency problem? Thanks again.