autoremove -f

aamir@aamir-pc:~$ sudo apt-get autoremove -f
Reading package lists... Done
Building dependency tree
Reading state information... Done
Correcting dependencies... Done
The following extra packages will be installed:
  libnm-glib2
The following packages will be REMOVED:
  extlinux syslinux-themes-debian syslinux-themes-debian-squeeze
The following NEW packages will be installed:
  libnm-glib2
0 upgraded, 1 newly installed, 3 to remove and 28 not upgraded.
Need to get 0 B/64.2 kB of archives.
After this operation, 238 kB disk space will be freed.
Do you want to continue [Y/n]? y
(Reading database ... 182573 files and directories currently installed.)
Removing extlinux ...
Removing syslinux-themes-debian ...
Removing syslinux-themes-debian-squeeze ...
Processing triggers for man-db ...
(Reading database ... 182497 files and directories currently installed.)
Unpacking libnm-glib2 (from .../libnm-glib2_0.8-0ubuntu3.3_i386.deb) ...
dpkg: error processing /var/cache/apt/archives/libnm-glib2_0.8-0ubuntu3.3_i386.deb (--unpack):
 trying to overwrite '/usr/lib/libnm-glib-vpn.so.1', which is also in package libnm-glib-vpn1 0.9.1.90-0ubuntu3
Errors were encountered while processing:
 /var/cache/apt/archives/libnm-glib2_0.8-0ubuntu3.3_i386.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)