Hi Yang,
Come to think of it, I got exactly the same BSoD error as Jim (BAD_POOL_CALLER).
However, my configuration is different (I have a bunch of VMware interfaces, and an Atheros AR9485WB-EG WLAN adaptor, which is also semi-supported by Acrylic Wi-Fi - but BSoDs for a different reason (seems to be related to NDIS drivers, with that)), and multiple loopback adaptors were created on my machine (named "Microsoft KM-TEST Loopback Adaptor", instead of "NPCap Loopback", if memory serves correctly).
Bizarrely, even after uninstalling NPCap, and replacing it with WinPCap, these KM-TEST adaptors still persist across reboots:
I assume that these are a side-effect of manually installing the .ini file, after attempting to run the set-up tool ("npfinstall -r", "npfinstall -li", and then "npfinstall -i") via a batch script with Administrator privileges.
I also found that although I could see packets containing a MAC address with the mnemonic "LOOP", I could not capture any ICMP traffic, when trying to ping 127.0.0.1, or ::1 (using both Microsoft Network Monitor, and Wireshark - the latter of which would not detect any interfaces, after reinstalling NPCap a few times, before eventually replacing it with WinPCap, until I rebooted).
If I get time, I'm going to see if I can reproduce the BSoD, and try writing down the steps involved.
Tyson.