Thanks Elhana. After I input 'apt-get purge amsn fm-boost', it says:
'rm cannot remove '/usr/share/applications/hildon/amsn.desktop':
No such file or directory
dpkg: error processing amsn (--remove):
subprocess post - removal script returned error exit status 1
Removing fm-boost ...
gtk-update-icon-cache: Cache file created sucessfully.
Errors were encountered while processing:
amsn
E: Sub-process /usr/bin/dpkg returned an error code (1)

Does this mean fm-boost have been removed but amsn failed to be removed?

BTW, how to copy the text from Xterm?

What should I do now?