Here is how to make Comodo Firewall working with Windows 8.1 Preview. It's simple! Run regedit, go to this value HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network On the right side you will see MaxNumFilters REG_DWORD change it's value from 1 to 8. Reboot your machine and then install Comodo Firewall or CIS, everything works just fine thereafter. If you don't have the above DWORD, you can simple create a new one by right click selecting New \ DWORD name it MaxNumFilters and change it's value to 8.