Please describe the problem that occured in more detail.
In general it's perfectly possible to copy a .deb file on another computer
and install it with
sudo dpkg -i path/to/yourfile.deb
There is one big problem: the package will probably have dependencies which
dpkg doesn't take account for.
In the case of a disconnected pc I recommend the Debian operating system with
only free repositories enabled because this way you can download all the
debian dvds which contains their whole repository and use apt for installing
software.
So you won't have to struggle with dependencies.
I don't know if trisquel has images of the whole repository, too.
