Some more explanations: these tilde-on-letter combinations are search patterns for aptitude. "~c" stands for packages already removed but not purged, there are some config files left on the system. See also "--purge --pending" in the man page of dpkg. So this does no harm if you don't intend to reinstall one of these packages.
Just to list these sort of packages command aptitude search '~c' "~ramd64" addresses all packages for architecture amd64, "~i" addresses all installed packages. The patterns can be combined, for example aptitude search '~c~ramd64' Could you show what this command lists? You said aptitude search '~i~ramd64' didn't list any package, which would mean there is no amd64 package installed on your system. Could you also show the outcome of dpkg -l | grep ':amd64' ? Regards, jvp.
