["Matt Richards" <knightrid@xxxxxxxxx>]

Error: "An error occurred while installing the Microsoft Network Monitor  Driver 
(NetMon) (0x800F0203). You will be able to use WinPcap on  standard 
network adapters, but not on Dialup connections and VPNs.  Please contact 
the WinPcap team."

I've been struggling with this error for the past 2 hours and I finally found a solution. Now I'm finally able to run GNS (Cisco emulator). I believe the problem stems from using a heavily customized version (i.e. stripped) of Windows XP SP2. First I tried uninstall Winpcap and installing the latest beta release which didn't help. Then I tried installing Windows XP Support Tool and running "c:\Program Files\Support Tools\netcap.exe", which failed to work. So that led me down a different route which was to install Microsoft Network Monitor 3.2 from: 

http://www.microsoft.com/downloads/details.aspx?FamilyID=f4db40af-1e08-4a21-a26b-ec2f4dc4190d&displaylang=en#filelist

After installing Netmon 3.2, I ran the program and everything launched without a problem. So I ran the Winpcap beta again. Note that I still got the error during installation, but I was able to run Dynamips. This finally allowed me to launch GNS and start using it. I know other people have run into this problem and I hope this information will help avoid reinstallations of Windows. 

Thanks,
Matt