If you use Windows 8 x64 and when you launch the Cisco VPN Client adapter and you see the following error:
Reason 442: Failed To Enable Virtual Adapter Here’s how to fix it.
Open your command prompt in Administrator mode by right clicking at the left lower corner of the screen and going to “Command Prompt (Administrator)”. You will have to log in as an administrator. Launch registry editor by typing “regedit.exe”. Browse to “HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\CVirtA“. In the DisplayName key, you will see something like @oem8.inf,%CVirtA_Desc%;Cisco Systems VPN Adapter. Edit that to just say Cisco Systems VPN Adapter. Try to connect again by launching the VPN Client. It should work!

I was using the vpnc the other day on my Backtrack 4 R2 system to log in to VPN. I noticed that there was nothing that would give me the status of whether or not the tunnel was up. So I wrote a small one-liner to help me:

while [ `ps aux |grep vpnc|grep -v grep|awk '{print $2}'` ] ; do printf "Connected\r"; done


I wanted to install Cisco VPN client on BackTrack3. You can get the Cisco VPN client source using the following command:
wget ftp://ftp.cs.cornell.edu/pub/rvr/upload/vpnclient-linux-4.8.00.0490-k9.tar.gz
tar zxvf vpnclient-linux-4.8.00.0490-k9.tar.gz
cd vpnclient/
wget http://tuxx-home.at/projects/cisco-vpnclient/vpnclient-linux-2.6.22.diff
patch < vpnclient-linux-2.6.22.diff
./vpn_install

I got this information from the following blog.
I ran into an error whereby the kernel sources were not found for the VPN client to install. I then got the BackTrack3 kernel sources.
cd /lib/
wget http://www.offensive-security.com/kernel.lzm
mkdir test
lzm2dir kernel.lzm test

Now go into the vpnclient directory and execute the following:
./vpn_install

Accept the defaults (except in my case I selected “No” on automatically start VPN client). When it asks for the sources point it to:
/lib/test/usr/src/linux-2.6.21.5

Then the VPN Client should compile without any issues. Then you just need to place your Cisco VPN client Profile (.pcf) in the /etc/opt/cisco-vpnclient/Profiles directory. You will need to first start the VPN client service first using:

/etc/init.d/vpnclient_init start

Once the service is started just connect using:

vpnclient connect mypcffile user test password <whatever>

Please note that the full name of the Profile file in the above case is mypcffile.pcf but I’ve deliberately excluded the .pcf extension.
This should work.