Comment 3 for bug 186552

as said i had downloaded packages from getdeb.net and ubuntu repo,though i take note of each dependencies,i get trouble,especially when it says
1)when installing third party apps and myth tv i get lots of trouble,the dependencies are not clear to understand,i.e some package name but i dont know whether its already installed or is this should be installed,where do i get that package.
by already installed meaning i.e is this package installed with ubuntu default system install or not.