The problem is mainly because users installed IP Blocker Firewall before installing Anti DDoS Guardian and they did not completely uninstall IP Blocker Firewall. In this case, the users need to completely uninstall Anti DDoS Guardian or IP Blocker First and then install Anti DDoS Guardian again. If the problem still exits, please manually remove all nblocker.sys files in your Windows systems before installing Anti DDoS Guardian.
If Anti DDoS Guardian was installed on Windows 2003 or Windows XP, then the problem may be caused by not allowing unsigned driver software. The following image shows the configuration of driver signing options in Windows XP. Please select "Ignore" or "Warn", do not choose "block". The "Driver Signing Options" dialog can be showed in Windows XP by following steps:
1. Right click "My Computer" icon and select "Properties" menu item.
2. "System Properties" window shows and select "Hardware" tab.
3. Click "Driver Signing" button.
This is becasue the current user does not have the privilege to write file on C:\Program Files(x86)\IP Blocker Firewall\ folder. You may change the privilege or reinstall this application on disk D:\ to avoid this error.