Windows NT and Win2000 has security in place that prohibits the use of real ICMP except for administrators. In order to get around this, you can set the UseICMPDll config property to true.

For older versions of IPWorks, in which the ability to use ICMP.dll is not present, the work around for NT is to disable the security check on RAW sockets by creating the following registry variable and settings its value to DWORD 1: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Afd\Parameters\DisableRawSecurity