When installing WinPcap 4.1.2 on Windows 7 I receive the following message

"A previous version of WinPcap has been detected on this system and cannot be
 removed because in use by another application.  Please close all the
 WinPcap-based applications and run the installer again."

I've installed and uninstalled the program several times.

According to the WinPcap FAQ one should:

Delete packet.* (packet.dll, packet.lib, etc.)

Delete wpcap.dll

Delete npf.sys.

This was done and it still wouldn't install.

Additionally, I've removed the Network Packet Filter 'device' using the device manager.

I also did a search in the registry for winpcap with no results. I searched for wpcap and found only one entry - a header file in an include directory. I renamed it to .old with no success.

Further, I downloaded the source code and searched for part of the message above hoping to find how it checks for previous versions. That string (version of WinPcap) was not found in the source code (using grep in cygwin).

Finally, I emailed the two people who are listed as contacts for the program.

I also tried installing the program as an Administrator.

No luck. You all are my last hope. :)

The question is as above - I want to remove the old version of WinPcap. But other questions that could help me are, how does a program check for previous versions? Is there something else I should be searching for in the registry? Is there a way to find out which program is using winpcap? Is there a way to see if any programs have a dependency on winpcap? Any leads would be greatly appreciated.


  • Why do you have a "Windows 8 include directory" in Win7?
    – Karan
    Jan 3 '13 at 19:55
  • Are you using Windows 7 or Windows 8? This is important information. Please remove any reference to the version of Windows your not using.
    – Ramhound
    Jan 3 '13 at 19:59
  • 1
    Karan, The Windows 8 include directory I mentioned is likely there due to using Visual Studio 2012 which has Windows 8 functionality. Ramhound, as noted in the first sentence - I am using Windows 7. As to why I mentioned it, I was trying to ensure everyone had as much information as possible. I was not trying to confuse anyone but I clearly did. Apologies. Do you have any suggestions I might try?
    – CramerTV
    Jan 3 '13 at 21:30

I resolved this issue on Windows 7 x64 by:

  1. opening a command prompt as administrator (Win+R > cmd > Enter)
  2. navigate to \windows\syswow64
  3. delete Packet.dll
  4. reboot
  5. Install new version of Winpcap
  • As I noted in the question I deleted packet.* which included packet.dll. It didn't work for me. My situation may have been unique.
    – CramerTV
    Feb 14 '14 at 21:46

While I never found a way to remove the old WinpCap my colleague suggested I boot up in safe mode in order to stop the mystery program from using it. Although I still got a warning that an old version was unable to be removed (and do I want to continue with the install?) the installation this time was successful.

So if you find yourself in this dilemma a possible workaround is to boot up in safe mode and install from there.


When I uninstalled some Netgear Wireless Adapter software, packet.dll was removed, enabling me to successfully install WinPcap.

  • This fixed my issue as well - I had some crummy Netgear USB software still installed, and it blocked WinPcap... uninstalling made it work, thanks!
    – agent86
    May 7 '15 at 23:54
  • Use Process Explorer feature Find Handle or DLL to find the application that is using Packet.dll file. In my case it was same Netgear wifi USB adapter software.
    – Casey
    Mar 2 '16 at 9:22

After the package removal, a reboot should be done before attempting to reinstall the package.

  • Thanks mdpc - rebooting is always good advice when finding strange problems but this time it has not helped. This is actually a very long standing problem for me. I first attempted using WinPcap (via Wireshark) 3 months ago and have simply been doing without it. I tried again yesterday with the same results but now I cannot just 'do without' anymore.
    – CramerTV
    Jan 3 '13 at 21:25

This worked for me.

Find and rename the following 2 files:

rename wpcap.dll to wpcap.dll.old

rename packet.dll to packet.dll.old

Try to reinstall WinpCap again.

  • I found that solution on the web, though it said to delete the files but alas, it didn't work for me.
    – CramerTV
    Nov 18 '13 at 23:18

as mentioned before, Packet.dll was being locked by another process. Windows 7 announces why it cannot be deleted when you try. Note which process has locked the dll and stop it (check Services and Processes) Remove the dll and restart the installation.

  • 1
    I did not receive an error when I deleted packet.dll. As I noted in the original post "According to the WinPcap FAQ I need to delete packet.* and wpcap.dll as well as npf.sys. Done." (and it didn't work)
    – CramerTV
    Nov 25 '13 at 18:22

I had this problem running Win 7 x86. Attempted upgrade from v4.1.2 to v4.1.3.

I uninstalled v4.1.2 succesfully using vanilla MS uninstall

Using the earlier post for x64 users as a guide I navigated to the folder containing the file packet.dll. For x86 users it is located in \windows\system32 and attempted to delete that file.

If there is an application relying on the packet.dll file you will not be able to delete it. Not so bad because you should also get a message telling you which application(s) is currently using packet.dll

Take note of that application. Open task manager. Go to services. Find the Application. Right click and stop the service.

Now you can install WinPcap successfully. In my case I did not need to do a reboot.

Lastly in task manager, restart any services you stopped previously.

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