1) Create a Restore Point using System Restore
2) Create a Repair disc (Recovery Drive in Win8.1):
Win 7 - Go to Start...All Programs...Maintenance...Create a System Repair Disc
Win 8 - Press "WIN" and "R" to open the Run dialog...type "RECDISC" (without the quotes) and press ENTER
Win 8.1 - Go to the Start Screen and type in "recoverydrive" (one word, without the quotes). That will start the recovery drive process. You will need a USB drive of at least 512 mB - and all data will be erased off of it. If copying the recovery partition the drive size will be much, much larger (16 - 32 gB drive required).
3) Test the System Repair disc/Recovery Drive to make sure that you can get to the System Restore entry when you boot from the disk/drive (you may also want to try actually using System Restore to make sure that it works)
4) Download this free program (
Autoruns for Windows) and use it to disable any instances of npf.sys (and anything that mentions WinPcap) that are starting (DO NOT DELETE - only disable by removing the checkmark in the left hand column)
5) Check in Device Manager (to include showing hidden devices from the View menu item) and ensure that any instances of npf.sys (and anything that mentions WinPcap) are "Uninstalled" (DO NOT DISABLE THESE).
6) Check in the Services applet (services.msc) to be sure any instances of npf.sys (and anything that mentions WinPcap) are disabled.
7) EXPERIMENTAL STEP (only try if you're certain of your abilities - I have not tried this step myself). Search the registry (use regedit.exe) to locate any entries that have the driver name (npf.sys) Also search for anything that mentions WinPcap. Delete these keys (it's advisable to back them up first - but you've also backed up the entire registry when creating a System Restore point in step 1. Alternatively, you can set the values in these keys to DISABLED (but the "how" of this is beyond the scope of this).
8) Go to C:\Windows\System32\drivers and rename the npf.sys driver to npf.
BAD (search the hard drive for it if it's not in C:\Windows\System32\drivers).
In the event that the system doesn't boot:
1) Boot from the System Repair disc/Recovery Drive and use the Command Prompt option to rename npf.BAD to npf.sys
Code:
ren C:\Windows\System32\drivers\npf.BAD C:\Windows\System32\drivers\npf.sys
21) Boot from the System Repair disc/Recovery Drive and use the System Restore option to restore the system to a point before the changes were made.
Good luck!