I've run into several situations where users in my office have tried to install software, such as vpn software, and the installation has failed due to exceeding the maximum number of filters allowed, as defined by the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network\MaxNumFilters. My understanding is that the default is 8 and the maximum is 14. I'd like to know if it is possible to get a count of the number of network filters currently installed on a system. For bonus points, I'd like to know if there is a way to determine what the filters are associated with: the installed software or dlls, something that could be useful in determining what could be uninstalled. I would hope this information would be useful to others.

Hi your question was already answered for you on Microsoft Answers: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network\MaxNumFilters that shows the maximum count. Further, if you look at: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network\{4d36e974-e325-11ce-bfc1-08002be10318}\ Each entry corresponds to a possible filter. Source: how can I find out how many network filter drivers I have using Windows 7 and uninstall if too many

Thanks, Jaap. It doesn't definitively answer my question, but it helps. The list of items under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network\{4d36e974-e325-11ce-bfc1-08002be10318} are only possible filters. According to http://msdn.microsoft.com/en-us/library/windows/hardware/ff553426%28v=vs.85%29.aspx the GUID 4d36e974-e325-11ce-bfc1-08002be10318 is described as "NetService". In my registry, some of the entries appear to be filters, and some do not. For example, HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network\{4d36e974-e325-11ce-bfc1-08002be10318}\{03F0DBAD-C963-4EB4-8510-DD8D23454D85} is described as "File and Printer Sharing for Microsoft Networks". I think it would count a s a service, but not as a filter, and consequently not count against MaxNumFilters. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network\{4d36e974-e325-11ce-bfc1-08002be10318}\{B5F4D659-7DAA-4565-8E41-BE220ED60542} on the other hand is described as "QoS Packet Scheduler" and has sub-keys (if that's the term) with the following names and values that indicate to me that it is an actual filter: [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network\{4d36e974-e325-11ce-bfc1-08002be10318}\{B5F4D659-7DAA-4565-8E41-BE220ED60542}\Ndi] "FilterClass"="scheduler" "FilterType"=dword:00000002 "FilterRunType"=dword:00000002 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network\{4d36e974-e325-11ce-bfc1-08002be10318}\{B5F4D659-7DAA-4565-8E41-BE220ED60542}\Ndi\Interfaces] "FilterMediaTypes"="ethernet, wan" Across all of the key entries that I see on my system, the only ones that seem consistently present and indicating a filter are Ndi\FilterClass and Ndi\Interfaces\FilterMediaTypes I have one entry on my system that has Ndi\FilterDeviceInfId, and neither of Ndi\FilterRunType and Ndi\FilterType. Now all I need is confirmation that only the entries that I think are filters count against MaxNumFilters.