Everyone has dealed with Cisco VPN Client on Vista probably knows the notorious Error 442 – Failed to enable virtual adapter. AFAIK this is a bug from Cisco that stays unfixed for at least 5 months (from the version 5.0.00.0340 released on May 2007 until now). Whether it is Cisco or Microsoft to point the finger at, i really don’t know.
So … you probably already tried this work-around suggestion from Cisco’s release notes:
Run cmd as Administrator and execute the following command:
reg add HKLM\System\CurrentControlSet\Services\Tcpip\Parameters /v ArpRetryCount /t REG_DWORD /d 0 /f
It just does not work ( at least every time i faced Error 442 ). What you should do is:
- Remove the client
- Activate the real Administrator account ( for detailed howto see this post )
- Restart, then log into the administrator account
- Install the file as normal ( right-click on it, choose “Run as Administrator”)
- After the installation finishes, restart again.
The client should work now. If not try to remove the Deterministic Network Enhancer protocol first, then reinstall VPN. Have patience, you will need to restart your computer sometimes.
Some people say the removal of Microsoft SQL do the trick (strange, erh ?), or simply turn on Media Sharing in the Network and Sharing Center. I haven’t tried this, so if it fixes your problem, then good for you.
If you could post your result here, then i am very appreciated 
Users’ comments:
From Nathan Le:
Under Services, I disabled Internet Connection Sharing (ICS) and then reboot. It then worked like a charm. By the way, I am using Windows Vista and Cisco VPN Client version 5.0.03.0560. Hope this helps.
From Chkrata:
The fix for 442 is simple – just tick ‘Allow Local LAN Access’ on the Transport tab of connection properties.
From fakh:
Many reasons that can cause this error, for instance if you have mcafee installed make sure you removed the NDIS filter under network, adaptors, choose the cicso vpn go to properties and uncheck NDIS.
From Chris:
The problem exists with MS Network Monitor and Vista. However, simply uninstalling NetMon will not solve the problem. Before uninstalling NetMon, run “nmconfig /uninstall” from the directory the application is installed. Once this is done you can uninstall Network Monitor. Reboot your system and all is right in the world!
From Tim:
I had this same problem start out of nowhere. After coming to this site and seeing some of the fixes, all I did was open C:\Program Files\Cisco Systems\VPN Client, right clicked on ipsecdialer.exe and vpngui.exe and clicked properties. I set both to run in xpSP2 compatibility mode and run as administrator. Problem was immediately fixed, no reinstallation was necessary and no DNE update was necessary. But yes I have to agree to let it run each time I start it.
Update: Updating DNE solves the problem indeed (uninstall VPN, get the latest DNE driver at deterministicnetworks.com, install it and then install VPN again). Deterministic Networks was acquired by Citrix, it’s site is redirected to Citrix’s
Update: If you happen to use the latest version (5.0.04.0300, as of Nov 2nd 2008) and still have this 442 error, uninstall the client and use an older version e.g. 5.0.03.0560
Update: In case the problem is stubborn and doesn’t want to go away, there is Shrewsoft VPN Client, which is compatible with many types of VPN gateway, and especially, free. It helped me many times when the Cisco client refused to run.
